feat(webui): sanctioned restart and graceful reload controls (Closes #642)

Adds a gated `system.restart_namespace` action so operators and workers can
restart or gracefully reload MCP namespaces through an authorized, audited
path instead of manual host process killing (#630).

- webui/sanctioned_restart.py: restart/reload operation model, dry-run
  intent preview, confirmation-string enforcement, audit emission, and
  post-restart health verification. Fails closed on unknown auth, missing
  capability, or ambiguous target namespace.
- webui/console_authz.py: RBAC entries for the restart capability with
  secret redaction preserved.
- webui/gated_actions.py: registers the restart action in the gated action
  framework so it cannot be invoked without capability + confirmation.
- task_capability_map.py: capability mapping for the restart operation.
- docs/sanctioned-restart-controls.md: operator documentation for the
  sanctioned path and the explicit prohibition on pkill recovery.
- docs/webui-authz-audit.md: audit model updated for restart events.
- tests/test_webui_sanctioned_restart.py: authorized preview, unauthorized
  deny, confirmation enforcement, contamination classification, and audit
  emission coverage.

No unrestricted kill path is exposed; manual pkill remains classified as
contamination and continues to block clean claims.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

docs/webui-authz-audit.md

@@ -91,6 +91,8 @@ already define, and a regression test asserts each mapping matches.
 | `close_pr` | controller | privileged | `gitea.pr.close` | Yes | No | No | 3 |
 | `merge_pr` | controller | privileged | `gitea.pr.merge` | Yes | **Yes** | **Yes** | 3 |
 | `delete_branch` | admin | destructive | `gitea.branch.delete` | Yes | **Yes** | **Yes** | 3 |
+| `system.reload_namespace` | controller | privileged | `runtime.reload_namespace` | Yes | No | No | 2 |
+| `system.restart_namespace` | admin | destructive | `runtime.restart_namespace` | Yes | **Yes** | **Yes** | 2 |
 
 **Dual control** means the acting principal may not be the sole authority: a
 second distinct principal must confirm. **Break-glass** means the action is
@@ -102,6 +104,13 @@ honouring it.
 `delete_branch` is admin-only rather than controller because it is the one
 irreversible action in the set.
 
+`system.restart_namespace` is admin-only for the same reason: restarting a
+namespace drops every in-flight request on it. `system.reload_namespace` drains
+first, so it is privileged but not destructive. Neither action is ever executed
+by the console — both hand off to a host supervisor, and neither exposes a raw
+process kill. See
+[`sanctioned-restart-controls.md`](sanctioned-restart-controls.md) (#642).
+
 ### Authorization decision
 
 `authorize(action_id, principal, for_execution=False)` returns a decision
@@ -199,8 +208,8 @@ breaking the request it describes.
 | Class | Applies to | Default |
 |-------|-----------|---------|
 | `standard` | Routine gated writes | 90 days |
-| `privileged` | `review_pr`, `close_pr`, and any unclassifiable action | 365 days |
-| `break_glass` | `merge_pr`, `delete_branch` | 730 days |
+| `privileged` | `review_pr`, `close_pr`, `system.reload_namespace`, and any unclassifiable action | 365 days |
+| `break_glass` | `merge_pr`, `delete_branch`, `system.restart_namespace` | 730 days |
 
 Each record carries its own class, day count, and computed `expires_at`, so
 retention is auditable per record rather than inferred from file age. An