[AAASM-3758] ✨ (hub): Add hub-level version/module switcher to docs landing

[Chisanan232]

Description

Adds a hub-level module + version switcher to the docs hub
(docs.agent-assembly.com). Per-module switchers were restored in #41/#42/#43,
but the hub landing itself had none — you had to open a module first to change
its version. This adds a persistent header on every hub page (rendered via
docs/theme/head.hbs, the same vanilla-JS widget-injection pattern as the
existing search / feedback / consent widgets) with a module dropdown and a
version/channel dropdown; selecting both navigates to
/<subpath>/<channel-or-tag>/.

It is driven entirely by the aggregated manifests the build already produces —
no hard-coded version strings:

• /modules.json — the build's own registry, now copied verbatim into public/
  by docs/scripts/aggregate.sh; the widget reads each module's name + subpath.
• /<module>/versions.json — the same manifest each module's own per-version
  switcher reads. The widget handles both shapes the aggregation emits: the
  mdBook {channels[], archived[]} shape (core) and the mike array
  [{version,title,aliases}] shape (python-sdk).

Graceful degradation (AC #4): a module with no versions.json (node-sdk,
go-sdk) is still listed and its option links to the module root; a hub built
standalone with no aggregation has no /modules.json and the widget silently
no-ops (exactly like the Pagefind search widget above it).

The per-module switcher logic is not touched, and no release-ordering
dependency is introduced.

Type of Change

• ✨ New section or feature documentation
• 🔧 Configuration / CI change

Related Issues

• Related Jira ticket: AAASM-3758

Documentation Checklist

• cd docs && mdbook build passes locally with no warnings
• All internal cross-links verified
• Page registered in docs/src/SUMMARY.md (N/A — header widget, not a new page)
• Self-hosted instructions not included (SaaS-only scope)
• "Last reviewed" footer updated (N/A — no content page edited)
• Commits follow GitEmoji convention and are small / atomic

How verified

• bash -n docs/scripts/aggregate.sh — syntax OK; cp $REGISTRY public/modules.json
  • a verify_manifest public/modules.json gate added to the existing
    manifest-presence checks.
• cd docs && mdbook build — hub renders; rendered index.html contains the
  .aa-modswitch widget; {{ path_to_root }} resolves correctly (ROOT='' at
  root domain).
• End-to-end: extracted the real widget script from the rendered HTML and ran
  it under a Node DOM shim against a local HTTP server serving a mini aggregated
  tree (real modules.json + core/python versions.json, node/go intentionally
  without one). Confirmed: module list = Core / Python SDK / Node SDK / Go SDK;
  core lists latest, pre-release, archived tags → /core/pre-release/;
  python lists mike versions+aliases → /python-sdk/<v>/; node/go fall back to
  /node-sdk/, /go-sdk/ roots.

Browser screenshot not attached — Chrome isn't available in this environment;
validated instead by running the actual widget code end-to-end under a Node DOM
shim against a live server (above).

🤖 Generated with Claude Code

https://claude.ai/code/session_01Cc1vBBiNxp9qLKQ5Gq85w8

[Chisanan232]

✅ Claude Code review — APPROVE-ready

CI: Aggregate all module docs green (the real end-to-end test — it clones every module, builds, and runs the full aggregation) + SonarCloud green.

Scope vs AAASM-3758: matches all four ACs.

• Hub landing gets a persistent module + version/channel switcher (docs/theme/head.hbs).
• Driven entirely by the aggregated manifests — /modules.json (newly emitted from the build's own registry) + each /<module>/versions.json — no hardcoded versions. Handles both manifest shapes the pipeline emits: mdBook {channels[],archived[]} and mike [{version,title,aliases}].
• Selecting module+version navigates to /<subpath>/<channel-or-tag>/; {{ path_to_root }} keeps it base-path-aware (root domain and github.io subpath).
• Graceful degradation: modules without versions.json (node/go today) still listed, fall back to module root; standalone hub build with no /modules.json silently no-ops.

Side-effect check: no regression. The widget lives in the hub's own mdBook theme head, so it affects only hub pages — the per-module subsites (built by their own toolchains) and their restored switchers are untouched. The aggregate.sh change is an additive cp modules.json public/ + a verify_manifest presence gate (consistent with the existing manifest checks); the green Aggregate run proves the gate passes and the pipeline still produces every module. No release-ordering dependency added. Injection pattern mirrors the existing search/feedback/consent widgets.

Validated by the agent: bash -n + mdbook build clean; widget extracted from rendered HTML and run under a Node DOM shim against a mini aggregated tree with real modules.json + core/python versions.json (node/go intentionally without) — module list and all navigation paths confirmed. (Browser screenshot not possible in-env; DOM-shim e2e used instead.)

Ready to merge. — Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud