hotfix(docs): README-page 404s, link previews, edit-this-page button (0.20.7)

[andrewjong]

Three docs-site changes in one 0.20.7 hotfix.

1. Every README-sourced page 404s

On the published 0.20 docs, https://docs.theairlab.org/0.20/tests/ and https://docs.theairlab.org/0.20/osmo/ (Reference → CI & Testing / OSMO Lab Admin Guide) return 404 — and so does every other page sourced from a file named README.md, including all autonomy package reference pages (e.g. /0.20/robot/ros_ws/src/local/planners/droan_local_planner/). Pages from non-README sources (e.g. tests/ci-cd-orchestrator.md) work fine.

Cause: Release 0.20.0 (#409) added the repo-root README.md to exclude_docs to keep it off the site. exclude_docs patterns are gitignore-style, so the unanchored name matches at every depth — silently excluding every README the same-dir plugin serves as a docs page.

Fix: anchor the pattern as /README.md so only the repo root is excluded, with a comment explaining the gitignore semantics.

2. Shared links preview as "Redirecting" (Slack/WhatsApp/iMessage)

Preview scrapers fetch raw HTML — no JS, no meta-refresh following — and every layer of the site lacked metadata:

• / (root) — bare mike set-default redirect stub titled "Redirecting"
• /0.20/ (version root) — bare mkdocs-redirects stub (index.md → docs/index.md) titled "Redirecting..."
• content pages — real titles but no og:*/description tags (Material only emits them via its social plugin, which we don't run)

Fix, one per layer:

• root: mike set-default -T with a custom template (.github/workflows/templates/root-redirect.html) — real title/description + OG/Twitter Card tags, same instant redirect via {{href}}
• version root: new post-build hook docs/hooks/social_meta_redirect_stub.py retitles the generated stub and injects the same meta block
• content pages: new theme override docs/overrides/main.html (block extrahead; home.html already extends main.html) adds per-page og:title/og:description/og:image + Twitter Card tags, and mkdocs.yml gains site_description

og:image is the 1600×900 splash poster served via the moving /main/ alias (mike copies real asset files into alias dirs — verified HTTP 200), so the absolute URL survives releases.

3. "Edit this page" button on every docs page

Enables Material's content.action.edit feature + edit_uri: each page shows a pencil icon linking to GitHub's editor for that page's source file. Contributors without write access automatically get GitHub's fork-and-propose flow. Since docs_dir is the repo root, edit_uri is just the branch prefix — it defaults to edit/main/ and the develop docs deploy overrides it to edit/develop/ via a DOCS_EDIT_URI env var (mkdocs !ENV). The landing page keeps no edit button by design (its home.html hero template has no content header).

Per the hotfix rule (#418): VERSION 0.20.6 → 0.20.7 with a dated release-notes section covering all three changes.

Verification

• pathspec.gitignore check: /README.md matches only the root README; nested ones no longer match.
• Edit links verified in the local build: README pages link to e.g. edit/main/tests/README.md, regular pages to their own .md source.
• Local mkdocs build: tests/, osmo/, ci-cd-orchestrator/, and package README pages all generated; the hook logged injected social meta into version-root redirect stub; home-page hero markup intact; per-page og:title correct (e.g. "System Test Suite - AirStack").
• The mike template rendered with Jinja2 (autoescape=True, href='0.20/') exactly as mike 2.2's set-default does — redirect and meta both correct.

Merging triggers deploy_docs_from_main.yaml, republishing the 0.20 slug and root in place. Note: previews for already-shared links stay stale until each app's link cache expires (Slack can be flushed per-URL via their debugger).

🤖 Generated with Claude Code

[github-actions]

Test Metrics — 169e388cdc65fabfc46afc92ab246886d670da9e

This was a unit/build-only run. Simulation regression comparison does not apply.

system.test_build_packages

Pass rates

Test	Pass	Fail	Skip	Rate
test_colcon_build_gcs	1	0	0	100%
test_colcon_build_ms_airsim	1	0	0	100%
test_colcon_build_robot	1	0	0	100%
test_colcon_test_robot	1	0	0	100%

Metrics

Test	Metric	Value
test_colcon_build_robot	duration_s	91.3s
test_colcon_test_robot	duration_s	41s
test_colcon_build_gcs	duration_s	67.15s
test_colcon_build_ms_airsim	duration_s	13.61s