docs: warn about unofficial PyPI packages and recommend version verification (#1982)

Clarify that only packages from github/spec-kit are official, and add
`specify version` as a post-install verification step to help users
catch accidental installation of an unrelated package with the same name.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: iamaeroplane

README.md

@@ -50,6 +50,8 @@ Spec-Driven Development **flips the script** on traditional software development
 
 Choose your preferred installation method:
 
+> **Important:** The only official, maintained packages for Spec Kit are published from this GitHub repository. Any packages with the same name on PyPI are **not** affiliated with this project and are not maintained by the Spec Kit maintainers. Always install directly from GitHub as shown below.
+
 #### Option 1: Persistent Installation (Recommended)
 
 Install once and use everywhere. Pin a specific release tag for stability (check [Releases](https://github.com/github/spec-kit/releases) for the latest):
@@ -62,7 +64,13 @@ uv tool install specify-cli --from git+https://github.com/github/spec-kit.git@vX
 uv tool install specify-cli --from git+https://github.com/github/spec-kit.git
 ```
 
-Then use the tool directly:
+Then verify the correct version is installed:
+
+```bash
+specify version
+```
+
+And use the tool directly:
 
 ```bash
 # Create new project

docs/installation.md

@@ -10,6 +10,8 @@
 
 ## Installation
 
+> **Important:** The only official, maintained packages for Spec Kit are published from the [github/spec-kit](https://github.com/github/spec-kit) GitHub repository. Any packages with the same name available on PyPI (e.g. `specify-cli` on pypi.org) are **not** affiliated with this project and are not maintained by the Spec Kit maintainers. Always install directly from GitHub as shown below.
+
 ### Initialize a New Project
 
 The easiest way to get started is to initialize a new project. Pin a specific release tag for stability (check [Releases](https://github.com/github/spec-kit/releases) for the latest):
@@ -69,6 +71,14 @@ uvx --from git+https://github.com/github/spec-kit.git@vX.Y.Z specify init <proje
 
 ## Verification
 
+After installation, run the following command to confirm the correct version is installed:
+
+```bash
+specify version
+```
+
+This helps verify you are running the official Spec Kit build from GitHub, not an unrelated package with the same name.
+
 After initialization, you should see the following commands available in your AI agent:
 
 - `/speckit.specify` - Create specifications