[formatting] Raise default width to 100 columns

[purefunctor]

Raises the formatter's default line width from 80 to 100 columns.

Why: 80 columns is narrower than modern editors and terminals comfortably support, so default-formatted output wraps more aggressively than most users want. 100 keeps lines readable while reducing forced breaks.

Approach: changes the single default in formatting::Config::default, which the CLI (--width fallback) and the language server (lineWidth fallback) both inherit. Help text, the formatting guide, and the two affected snapshots are updated; all other fixtures either pin an explicit width or already fit, so output is unchanged for them.

Verification: cargo check -p formatting --tests, -p iris-cli, -p iris-lsp-workspace; just t formatting, just t docs, just t lsp (no pending snapshots); E2E formatting + lsp suites (25 tests) and the CLI help snapshot test pass; just format and git diff --check clean.

Thread: https://ampcode.com/threads/T-01a11720-fd70-73ae-a723-70ad4084ac5b

[purefunctor]

Granite Review

Council

Role	Mode	Status	Attempt	Amp thread
Council member	review-gpt-6-luna	completed	1	T-01a118dc-2fa9-75af-bdde-3921b1b7e9f7
Council member	review-gpt-6-sol	completed	1	T-01a118dc-308f-723e-9707-7613e505fac1
Synthesis	review-astra-synthesis	completed	1	T-01a118f8-af24-764c-b326-f8c71865ae1d

Findings

No actionable findings.

[github-actions]

Compatibility regression report

Package set 81.3.0 for PureScript 0.15.15.

✅ The candidate introduces no compatibility errors.

Diagnostic class	Base	Candidate	Introduced	Fixed
Compiler errors	0	0	0	0
Compiler warnings	36	36	0	0
Verifier errors	0	0	0	0

Introduced errors

None.

Fixed errors (0)

None.

Warning changes (0 introduced, 0 fixed)

Introduced

None.

Fixed

None.

Candidate errors (0)

None.

Candidate warnings (36)

• deno@0.0.5/src/Deno.purs:38:17 — CustomWarning (checking): Data.Map's `Semigroup` instance is now unbiased and differs from the left-biased instance defined in PureScript releases <= 0.13.x.
• deno@0.0.5/src/Deno/Dotenv.purs:41:20 — CustomWarning (checking) × 2: Data.Map's `Semigroup` instance is now unbiased and differs from the left-biased instance defined in PureScript releases <= 0.13.x.
• deno@0.0.5/src/Deno/Http/Request.purs:47:25 — CustomWarning (checking): Data.Map's `Semigroup` instance is now unbiased and differs from the left-biased instance defined in PureScript releases <= 0.13.x.
• literals@1.0.2/src/Literals/Null.purs:11:1 — UnparseableFFIModule (javascript): Oxc could not parse the JavaScript FFI module. Fix the invalid or unsupported JavaScript syntax; Iris treated the module as opaque and skipped export-name validation: Unexpected token
• react-basic-dom-beta@0.1.1/src/Beta/DOM.purs:33:31 — DuplicateImport (indexing): Import list contains multiple references to 'Proxy'
• sparse-polynomials@3.0.1/src/Data/Sparse/Polynomial.purs:1048:1 — MissingPatterns (checking) × 2: Pattern match is not exhaustive. Missing: _
• text-formatting@0.1.0/src/Data/Text/Format/Dodo/Printer.purs:64:25 — CustomWarning (checking) × 23: Debug function usage
• trivial-unfold@0.5.0/src/Data/Unfoldable1/Trivial1.purs:150:17 — MissingPatterns (checking): Pattern match is not exhaustive. Missing: Right _
• xterm@1.0.0/src/XTerm/UnicodeHandling.purs:15:1 — UnparseableFFIModule (javascript) × 2: Oxc could not parse the JavaScript FFI module. Fix the invalid or unsupported JavaScript syntax; Iris treated the module as opaque and skipped export-name validation: Expected a semicolon or an implicit semicolon after a statement, but found none
• yoga-react-dom@2.0.1/src/Yoga/React/DOM.purs:34:31 — DuplicateImport (indexing): Import list contains multiple references to 'Proxy'
• yoga-tree-utils@1.0.0/src/Yoga/Tree/Extended/Path.purs:20:72 — DuplicateImport (indexing): Import list contains multiple references to 'snoc'

View workflow run

[claude]

Review against AGENTS.md: no issues found.

The default lives in formatting::Config::default, which is the layer that owns it, and both the CLI (--width) and the LSP (lineWidth) fall back to it. The two snapshot changes, the CLI help and the invalid_formatting_options report, now show the new default as intended. The assertion_line change matches where the harness asserts the snapshot now, so the snapshot was regenerated, not edited by hand. I found no other places in the docs or editor config that still say the default is 80; the remaining 80s are explicit @format width=80 pins in fixtures, or hover and progress widths that have nothing to do with the formatter.

Checks run:

• cargo check -p formatting --tests: passed
• cargo check -p iris-cli -p iris-lsp-workspace --tests: passed
• cargo nextest run -p formatting: no unit tests in the crate
• just t formatting: all passed, no pending snapshots
• just format --check: clean
• just licenses, then git status: THIRDPARTY.toml unchanged, working tree clean, no .snap.new files
• E2E (cli__help_format, formatting suite): not run here. The pinned Spago tooling (just e2e-prepare) isn't installed in this environment, so these rely on the Cargo Build & Test workflow.