Port .devcontainer/docs/ to docs site (#32)

* Port .devcontainer/docs/ to docs site and remove legacy directory

Merge 5 legacy reference docs from .devcontainer/docs/ into the
Starlight documentation site at docs/:

- New Keybindings page (Customization) — VS Code/Claude Code shortcut
  conflicts, resolution options, and full keybinding reference
- New Troubleshooting page (Reference) — 12+ problem/solution entries
  for build, auth, plugins, performance, and reset procedures
- New Optional Features page (Customization) — mcp-qdrant vector memory
  setup guide and feature disabling
- Merged setup variables (.env flags) into Environment Variables ref
- Merged .secrets authentication docs into Configuration page
- Updated sidebar navigation with 3 new entries
- Removed .devcontainer/docs/ (all content now in docs site)

* Fix changelog wording: "merged" → "migrated content from"

One of the 5 legacy docs (plugins.md) was superseded rather than
merged, making "merged" inaccurate.

---------

Co-authored-by: AnExiledDev <AnExiledDev@users.noreply.github.com>

Author: AnExiledDev

.devcontainer/CHANGELOG.md

@@ -11,6 +11,13 @@
 - Updated prerequisites and installation docs to support all DevContainer clients (VS Code, CLI, JetBrains Gateway, DevPod, Codespaces)
 - Added tabbed client-specific instructions on the installation page
 - Added dedicated port forwarding reference page covering VS Code auto-detect, devcontainer-bridge, and SSH tunneling
+- **Ported `.devcontainer/docs/` to docs site** — migrated content from 5 legacy reference docs into the Starlight documentation site:
+  - New **Keybindings** page (Customization) — VS Code/Claude Code shortcut conflicts and resolution options
+  - New **Troubleshooting** page (Reference) — 12+ problem/solution entries for build, auth, plugins, and performance issues
+  - New **Optional Features** page (Customization) — mcp-qdrant vector memory setup guide
+  - Merged setup variables (`.env` flags) into the Environment Variables reference
+  - Merged `.secrets` file authentication docs into the Configuration page
+- Removed `.devcontainer/docs/` directory — all content now lives in the docs site
 
 ### Fixed