docs(feat[gp-sphinx]): Migrate conf.py to merge_sphinx_config()

why: libtmux was maintaining ~290 lines of Sphinx configuration that
     duplicates what gp-sphinx now provides as shared defaults — fonts,
     theme, extensions, copybutton, autodoc, and linkcode resolution.
what:
- Replace manual conf.py with merge_sphinx_config() and make_linkcode_resolve()
- Retain project-specific overrides: announcement banner, favicon,
  custom CSS, todo extension

Author: tony

docs/conf.py

@@ -1,289 +1,54 @@
-# flake8: NOQA: E501
 """Sphinx configuration for libtmux."""
 
 from __future__ import annotations
 
-import contextlib
-import inspect
 import pathlib
 import sys
-import typing as t
-from os.path import relpath
 
 import libtmux
 
-if t.TYPE_CHECKING:
-    from sphinx.application import Sphinx
+from gp_sphinx.config import make_linkcode_resolve, merge_sphinx_config
 
 # Get the project root dir, which is the parent dir of this
 cwd = pathlib.Path(__file__).parent
 project_root = cwd.parent
 project_src = project_root / "src"
 
 sys.path.insert(0, str(project_src))
-sys.path.insert(0, str(cwd / "_ext"))
 
 # package data
 about: dict[str, str] = {}
 with (project_src / "libtmux" / "__about__.py").open() as fp:
     exec(fp.read(), about)
 
-extensions = [
-    "sphinx.ext.autodoc",
-    "sphinx_pytest_fixtures",
-    "sphinx_fonts",
-    "sphinx.ext.intersphinx",
-    "sphinx_autodoc_typehints",
-    "sphinx.ext.todo",
-    "sphinx.ext.linkcode",
-    "sphinx.ext.napoleon",
-    "sphinx_inline_tabs",
-    "sphinx_copybutton",
-    "sphinxext.opengraph",
-    "sphinxext.rediraffe",
-    "myst_parser",
-    "linkify_issues",
-    "sphinx_design",
-]
-
-myst_enable_extensions = [
-    "colon_fence",
-    "substitution",
-    "replacements",
-    "strikethrough",
-    "linkify",
-]
-
-myst_heading_anchors = 4
-
-templates_path = ["_templates"]
-
-source_suffix = {".rst": "restructuredtext", ".md": "markdown"}
-
-master_doc = "index"
-
-project = about["__title__"]
-project_copyright = about["__copyright__"]
-
-version = "{}".format(".".join(about["__version__"].split("."))[:2])
-release = "{}".format(about["__version__"])
-
-exclude_patterns = ["_build"]
-
-pygments_style = "monokai"
-pygments_dark_style = "monokai"
-
-html_favicon = "_static/favicon.ico"
-html_static_path = ["_static"]
-html_css_files = ["css/custom.css"]
-html_extra_path = ["manifest.json"]
-html_theme = "furo"
-html_theme_path: list[str] = []
-html_theme_options: dict[str, str | list[dict[str, str]]] = {
-    "light_logo": "img/libtmux.svg",
-    "dark_logo": "img/libtmux.svg",
-    "footer_icons": [
-        {
-            "name": "GitHub",
-            "url": about["__github__"],
-            "html": """
-                <svg stroke="currentColor" fill="currentColor" stroke-width="0" viewBox="0 0 16 16">
-                    <path fill-rule="evenodd" d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0 0 16 8c0-4.42-3.58-8-8-8z"></path>
-                </svg>
-            """,
-            "class": "",
-        },
-    ],
-    "source_repository": f"{about['__github__']}/",
-    "source_branch": "master",
-    "source_directory": "docs/",
-    "announcement": "<em>Friendly reminder:</em> 📌 Pin the package, libtmux is pre-1.0 and APIs will be <a href='/migration.html'>changing</a> throughout 2026.",
-}
-html_sidebars = {
-    "**": [
-        "sidebar/scroll-start.html",
-        "sidebar/brand.html",
-        "sidebar/search.html",
-        "sidebar/navigation.html",
-        "sidebar/projects.html",
-        "sidebar/scroll-end.html",
-    ],
-}
-
-# linkify_issues
-issue_url_tpl = f"{about['__github__']}/issues/{{issue_id}}"
-
-# sphinx.ext.autodoc
-autoclass_content = "both"
-autodoc_member_order = "bysource"
-# Automatically extract typehints when specified and place them in
-# descriptions of the relevant function/method.
-autodoc_typehints = "description"
-# Don't show class signature with the class' name.
-autodoc_class_signature = "separated"
-toc_object_entries_show_parents = "hide"
-
-# sphinx-autodoc-typehints
-# Suppress warnings for forward references that can't be resolved
-# (types in TYPE_CHECKING blocks used for circular import avoidance)
-suppress_warnings = [
-    "sphinx_autodoc_typehints.forward_reference",
-]
-
-# sphinx-copybutton
-copybutton_prompt_text = (
-    r">>> |\.\.\. |> |\$ |\# | In \[\d*\]: | {2,5}\.\.\.: | {5,8}: "
-)
-copybutton_prompt_is_regexp = True
-copybutton_remove_prompts = True
-copybutton_line_continuation_character = "\\"
-
-# sphinxext-rediraffe
-rediraffe_redirects = "redirects.txt"
-rediraffe_branch = "master~1"
-
-# sphinxext.opengraph
-ogp_site_url = about["__docs__"]
-ogp_image = "_static/img/icons/icon-192x192.png"
-ogp_site_name = about["__title__"]
-
-# sphinx_fonts — self-hosted IBM Plex via Fontsource CDN
-sphinx_fonts = [
-    {
-        "family": "IBM Plex Sans",
-        "package": "@fontsource/ibm-plex-sans",
-        "version": "5.2.8",
-        "weights": [400, 500, 600, 700],
-        "styles": ["normal", "italic"],
-        "subsets": ["latin", "latin-ext"],
-    },
-    {
-        "family": "IBM Plex Mono",
-        "package": "@fontsource/ibm-plex-mono",
-        "version": "5.2.7",
-        "weights": [400, 500, 600, 700],
-        "styles": ["normal", "italic"],
-        "subsets": ["latin", "latin-ext"],
+conf = merge_sphinx_config(
+    project=about["__title__"],
+    version=about["__version__"],
+    copyright=about["__copyright__"],
+    source_repository=f"{about['__github__']}/",
+    docs_url=about["__docs__"],
+    source_branch="master",
+    light_logo="img/libtmux.svg",
+    dark_logo="img/libtmux.svg",
+    extra_extensions=["sphinx_pytest_fixtures", "sphinx.ext.todo"],
+    intersphinx_mapping={
+        "python": ("https://docs.python.org/", None),
+        "pytest": ("https://docs.pytest.org/en/stable/", None),
     },
-]
-
-sphinx_font_preload = [
-    ("IBM Plex Sans", 400, "normal"),  # body text
-    ("IBM Plex Sans", 700, "normal"),  # headings
-    ("IBM Plex Mono", 400, "normal"),  # code blocks
-]
-
-sphinx_font_fallbacks = [
-    {
-        "family": "IBM Plex Sans Fallback",
-        "src": 'local("Arial"), local("Helvetica Neue"), local("Helvetica")',
-        "size_adjust": "110.6%",
-        "ascent_override": "92.7%",
-        "descent_override": "24.9%",
-        "line_gap_override": "0%",
+    linkcode_resolve=make_linkcode_resolve(
+        libtmux, about["__github__"], src_dir="src"
+    ),
+    # Project-specific overrides
+    theme_options={
+        "announcement": (
+            "<em>Friendly reminder:</em> 📌 Pin the package, libtmux is"
+            " pre-1.0 and APIs will be <a href='/migration.html'>changing</a>"
+            " throughout 2026."
+        ),
     },
-    {
-        "family": "IBM Plex Mono Fallback",
-        "src": 'local("Courier New"), local("Courier")',
-        "size_adjust": "100%",
-        "ascent_override": "102.5%",
-        "descent_override": "27.5%",
-        "line_gap_override": "0%",
-    },
-]
-
-sphinx_font_css_variables = {
-    "--font-stack": '"IBM Plex Sans", "IBM Plex Sans Fallback", -apple-system, BlinkMacSystemFont, sans-serif',
-    "--font-stack--monospace": '"IBM Plex Mono", "IBM Plex Mono Fallback", SFMono-Regular, Menlo, Consolas, monospace',
-    "--font-stack--headings": "var(--font-stack)",
-}
-
-intersphinx_mapping = {
-    "python": ("https://docs.python.org/", None),
-    "pytest": ("https://docs.pytest.org/en/stable/", None),
-}
-
-
-def linkcode_resolve(domain: str, info: dict[str, str]) -> None | str:
-    """
-    Determine the URL corresponding to Python object.
-
-    Notes
-    -----
-    From https://github.com/numpy/numpy/blob/v1.15.1/doc/source/conf.py, 7c49cfa
-    on Jul 31. License BSD-3. https://github.com/numpy/numpy/blob/v1.15.1/LICENSE.txt
-    """
-    if domain != "py":
-        return None
-
-    modname = info["module"]
-    fullname = info["fullname"]
-
-    submod = sys.modules.get(modname)
-    if submod is None:
-        return None
-
-    obj = submod
-    for part in fullname.split("."):
-        try:
-            obj = getattr(obj, part)
-        except Exception:  # noqa: PERF203
-            return None
-
-    # strip decorators, which would resolve to the source of the decorator
-    # possibly an upstream bug in getsourcefile, bpo-1764286
-    try:
-        unwrap = inspect.unwrap
-    except AttributeError:
-        pass
-    else:
-        if callable(obj):
-            obj = unwrap(obj)
-
-    try:
-        fn = inspect.getsourcefile(obj)
-    except Exception:
-        fn = None
-    if not fn:
-        return None
-
-    try:
-        source, lineno = inspect.getsourcelines(obj)
-    except Exception:
-        lineno = None
-
-    linespec = f"#L{lineno}-L{lineno + len(source) - 1}" if lineno else ""
-
-    fn = relpath(fn, start=pathlib.Path(libtmux.__file__).parent)
-
-    if "dev" in about["__version__"]:
-        return "{}/blob/master/{}/{}/{}{}".format(
-            about["__github__"],
-            "src",
-            about["__package_name__"],
-            fn,
-            linespec,
-        )
-    return "{}/blob/v{}/{}/{}/{}{}".format(
-        about["__github__"],
-        about["__version__"],
-        "src",
-        about["__package_name__"],
-        fn,
-        linespec,
-    )
-
-
-def remove_tabs_js(app: Sphinx, exc: Exception) -> None:
-    """Remove tabs.js from _static after build."""
-    # Fix for sphinx-inline-tabs#18
-    if app.builder.format == "html" and not exc:
-        tabs_js = pathlib.Path(app.builder.outdir) / "_static" / "tabs.js"
-        with contextlib.suppress(FileNotFoundError):
-            tabs_js.unlink()  # When python 3.7 deprecated, use missing_ok=True
-
-
-def setup(app: Sphinx) -> None:
-    """Configure Sphinx app hooks."""
-    app.add_js_file("js/spa-nav.js", loading_method="defer")
-    app.connect("build-finished", remove_tabs_js)
+    html_favicon="_static/favicon.ico",
+    html_css_files=["css/custom.css"],
+    html_extra_path=["manifest.json"],
+    rediraffe_redirects="redirects.txt",
+)
+globals().update(conf)