feat: refresh shared Git config mounts live

- Use profile-scoped canonical Git clone sources with locked refreshes
- Mount shared Git configuration read-only and isolate profile content
- Add API and desktop/mobile actions for live Git mount refresh

Quality gates: frontend build and backend py_compile passed.
Skipped: backend pytest/Ruff unavailable; Docker/manual checks not approved.

openspec/changes/live-git-config-mount-refresh/change.md

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+# Live Git Config Mount Refresh
+
+## Why
+
+Git-backed Config Profile mounts are currently cloned per instance. Their content cannot be refreshed consistently for running sessions, and writable container mounts can dirty the checkout.
+
+## Change
+
+Move Git Config Profile mounts to profile-scoped canonical host clones. Bind the already-mounted directory sources read-only into compatible instances and refresh a stable branch/ref checkout in place under a per-clone lock.
+
+## Scope
+
+- Canonical clone identity: profile, normalized remote, requested ref, and credential scope.
+- In-place refresh for existing directory mounts only.
+- Explicit outcomes for live refresh, restart-required topology changes, and refresh failures.
+- Read-only container Git config mounts.
+
+## Out of scope
+
+- Writable shared Git configuration mounts.
+- Global cross-user clone sharing.
+- Live mount-topology changes, direct-file mappings, or glob match-set changes.
+- Atomic all-files revision switching for processes already reading the mount.