feat(mcp): Connectors — catalog + global vs per-user runtimes (§7/§14/§15)

Re-architects MCP from one owner table + agent-written registration into an
admin-curated catalog with two runtimes unioned per session, surfaced in the UI
as "Connectors" (mcp/schema stays neutral, §0.1).

Two runtimes behind one seam (§7):
- Global runtime: shared, stateless connectors (web-search, Tavily…) on the
  HOST, connected at boot from mcp_global_servers, access-filtered per user via
  mcp_global_access.
- Per-user runtime: a user's activated connectors run INSIDE their container,
  started at first login from mcp_user_servers and living until restart (§9);
  docker exec -i children die via kill_on_drop when the UserContext drops.
- McpProvider trait (mcp/provider.rs): the session round-loop never learns which
  runtime owns a server. McpManager implements it directly (inert ownerless
  bundle); UserMcpView implements global ∪ user with an accessible_global
  snapshot. Both share McpManager::connect_all; McpServerSpec +
  global_row_spec/user_row_spec turn a DB row into a connectable spec.
- mcp-client: McpServerConfig.launch_in runs a stdio command inside a container
  via docker exec -i (set at runtime, never parsed from config).

Authorization is a capability on the role, not `if role==admin` (§0.1/§14):
role_capabilities table + db/role_capabilities.rs — register_remote and
register_local_from_catalog are self-service (seeded on every new role), while
register_local_script and manage_catalog are admin-only. admin holds every
capability by construction. This removes the agent-facing register_mcp/delete_mcp
tools and the mcp kinds of list_items/toggle_item, closing the §14 RCE vector.

Schema:
- Registry: mcp_catalog (vetted templates — schema only, no live creds),
  mcp_global_servers + mcp_global_access, role_capabilities.
- Owner: mcp_user_servers (per-user activations; api_key encrypted at rest,
  catalog_name a bare TEXT snapshot, never an owner→registry FK).
- Drops the old owner table mcp_servers.

API + UI: src/frontend/api/mcp.rs (admin catalog/global/access + user
available/activate/activated, all capability-gated via require_cap);
web/components/connectors.js (<connectors-page>) renders the user view always
and the admin view for role_id === 'admin'.

Deferred: interactive per-user auth (OAuth callback / QR / SSH elicitation, §15)
— only none/api_key wired; no boot seed of catalog presets; per-(user, session)
MCP grant model still open.

src/frontend/api/mod.rs

@@ -128,8 +128,19 @@ pub fn router() -> Router<Arc<Skald>> {
         .route("/tool-permission-groups/{id}/duplicate",     post(run_context::duplicate_group))
         // Session tool_group assignment (runtime)
         .route("/sessions/{session_id}/run-context", put(run_context::set_session_run_context))
-        // MCP
+        // MCP / Connectors (blueprint §14/§15)
         .route("/mcp/servers",                  get(mcp::list_servers))
+        // admin: catalog + globally-active connectors
+        .route("/mcp/catalog",                  get(mcp::catalog_list).post(mcp::catalog_upsert))
+        .route("/mcp/catalog/{id}",             delete(mcp::catalog_delete))
+        .route("/mcp/global",                   get(mcp::global_list).post(mcp::global_enable))
+        .route("/mcp/global/{id}",              delete(mcp::global_delete))
+        .route("/mcp/global/{id}/access",       get(mcp::global_get_access).put(mcp::global_set_access))
+        // user: available catalog + per-user activation
+        .route("/mcp/available",                get(mcp::available))
+        .route("/mcp/activate",                 post(mcp::activate))
+        .route("/mcp/activated",                get(mcp::activated_list))
+        .route("/mcp/activated/{id}",           delete(mcp::deactivate))
         // Dev / debug
         .route("/dev/debug_mode",               get(dev::get_debug_mode).post(dev::set_debug_mode).put(dev::set_debug_mode))
         .route("/dev/llm-requests",             get(dev::list_llm_requests))
@@ -179,6 +190,10 @@ impl ApiError {
     pub fn unauthorized(msg: impl Into<String>) -> Self {
         Self { status: StatusCode::UNAUTHORIZED, message: msg.into() }
     }
+
+    pub fn forbidden(msg: impl Into<String>) -> Self {
+        Self { status: StatusCode::FORBIDDEN, message: msg.into() }
+    }
 }
 
 /// Resolves the authenticated caller's per-user runtime context, or `401` when the