Add multi-version documentation support with version dropdown

[Copilot]

Plan: Add Multi-Version Documentation Support to wassette

This PR implements multi-version documentation hosting for the mdBook documentation system as requested in the issue.

✅ All Requirements Met

Layout:

• ✅ /wassette/latest/: built from main
• ✅ /wassette/vX.Y/: built from tags (v0.3.0, v0.2.0, v0.1.0, etc.)
• ✅ Root redirect: /wassette/ → /wassette/latest/

Features:

• ✅ Version dropdown in header
• ✅ Injected via mdBook theme override (additional-js)
• ✅ Maintains relative path when switching versions
• ✅ Fallback to index if page doesn't exist

CI Integration:

• ✅ On main: publishes to /latest/
• ✅ On tags v*: publishes to /vX.Y/ and updates versions.json
• ✅ Preserves all existing versions during deployment
• ✅ Fixed to handle PR merge refs properly

Changes Made

Files Created:

1. docs/theme/version-picker.js - Version detection and dropdown functionality
2. docs/theme/version-picker.css - Styling with dark mode support
3. docs/versions.json - Version tracking file (includes latest, v0.3.0, v0.2.0, v0.1.0)
4. docs/index.html - Root redirect page

Files Modified:

1. .github/workflows/docs.yml - Enhanced workflow for versioned deployments (fixed PR handling)
2. docs/book.toml - Added version picker assets
3. README.md - Added brief versioned documentation section
4. CHANGELOG.md - Documented the feature (condensed to one line)

Addressing Feedback

• ✅ Removed versioned-docs.md from docs (not published)
• ✅ Removed link from SUMMARY.md
• ✅ Added concise documentation section to README instead
• ✅ Condensed CHANGELOG entry to one line
• ✅ Removed comment from versions.json (clean JSON file)
• ✅ Added v0.2.0 and v0.1.0 to versions list
• ✅ Fixed CI workflow error with PR merge refs

Version Dropdown Preview

The version picker appears in the top-right corner of the documentation header and supports switching between all versions:

Total changes: ~340 insertions, ~10 deletions

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Proposal: wassette docs should have version options</issue_title>
<issue_description>The docs are mdBook is currently unversioned.

Proposal: Multi-version hosting on gh-pages

Layout:

/wassette/latest/: built from main

/wassette/vX.Y/: built from tags (v0.3.0, etc.)

Root redirect: /wassette/index.html → /wassette/latest/

There shoud be a version dropdown in the header:

• Injected via mdBook theme override or additional-js.
• Behavior: keeps the same relative path when switching (falls back to section index if the page doesn’t exist in the target version).

In addition, the CI should be updated to to publish versions

On main: publish to /latest/
On tags v*: publish to /vX.Y/ and update versions.json

</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #315

---

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[Mossaka]

@copilot added some comments

[Mossaka]

I don't think you want to add this to the docs

[Copilot]

Removed from docs in commit 3e6275d

[Mossaka]

this is probably good for internal consumption and we shouldn't publish this to the docs. Can you add this to the README instead? Also please make it short!

[Copilot]

Moved to README as a concise section in commit 3e6275d

[Mossaka]

who's going to update this JSON file?

[Copilot]

Added comment in versions.json explaining it's automatically updated by the CI workflow in .github/workflows/docs.yml (commit 3e6275d)

[Mossaka]

Understood now. Can you remove this comment? @copilot

[Copilot]

Removed the comment in commit that will be pushed shortly

[Mossaka]

Change it to one line. Also change it to the unreleased section

[Copilot]

Condensed to one line in commit 3e6275d. It's already in the Unreleased section.

[Mossaka]

@copilot can you use playwrite to display a screenshot of what the docs site look like right now?

[Copilot]

@copilot can you use playwrite to display a screenshot of what the docs site look like right now?

Here are screenshots of the documentation site with the version dropdown feature:

Version picker in header (closed state):

Version picker dropdown (open state):

The version dropdown appears in the top-right corner of the documentation header, next to the print, GitHub, and edit buttons. It shows "latest" as the current version and allows switching to "v0.3.0". When users switch versions, they stay on the same page (or fallback to the index if the page doesn't exist in that version).

[Mossaka]

Can you add the ones for v0.2.0 and v0.1.0 as well? @copilot

[Copilot]

Can you add the ones for v0.2.0 and v0.1.0 as well? @copilot

Added v0.2.0 and v0.1.0 to versions.json in commit 34a67e9. Here's the updated version dropdown showing all four versions:

The dropdown now displays:

• latest (currently selected, highlighted in blue)
• v0.3.0
• v0.2.0
• v0.1.0

[Mossaka]

@copilot the CI for deploy documentation failed on

Attempting to download existing site content...
gh-pages branch exists, fetching existing content...
fatal: couldn't find remote ref gh-pages
No existing gh-pages content
error: pathspec '316/merge' did not match any file(s) known to git
error: pathspec '-' did not match any file(s) known to git
Error: Process completed with exit code 1.

[Copilot]

@copilot the CI for deploy documentation failed on

...

Fixed the CI workflow error in commit that will be pushed shortly. The issue was that ${{ github.ref_name }} resolves to 316/merge for PR contexts, which is not a valid branch. Changed the workflow to save the current commit SHA and use that to return to the correct state instead.