fix: authoritative cross-role generic queue allocation (Closes #840)

Add controller-owned cross_role allocation mode that inspects the full
queue and returns one selection with required role/profile/action and
lease evidence. Document process_work_queue routing, normalize
controller role metadata, and keep the dashboard explanatory only.

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

role_session_router.py

@@ -81,6 +81,12 @@ AUTHOR_TASKS = frozenset({
     "reconcile_landed_pr",
 })
 
+CONTROLLER_TASKS = frozenset({
+    "process_work_queue",
+    "process-work-queue",
+    "cross_role_allocate",
+})
+
 RECONCILER_TASKS = frozenset({
     "cleanup_merged_pr_branch",
     # #729: delete_branch is reconciler-owned (gitea.branch.delete is granted
@@ -132,6 +138,10 @@ TASK_REQUIRED_ROLE = {
     "reconcile_close_superseded_pr": "reconciler",
     "reconcile_close_satisfied_issue": "reconciler",
     "reconcile_create_followup_issue": "reconciler",
+    # #840: controller-owned generic queue allocation / routing.
+    "process_work_queue": "controller",
+    "process-work-queue": "controller",
+    "cross_role_allocate": "controller",
 }
 
 WRONG_ROLE_REVIEWER_MSG = (
@@ -147,6 +157,10 @@ WRONG_ROLE_MERGER_MSG = (
     "Wrong role/session for merger task. Launch merger MCP namespace."
 )
 
+WRONG_ROLE_CONTROLLER_MSG = (
+    "Wrong role/session for controller task. Launch controller MCP namespace."
+)
+
 _session_last_route: dict | None = None
 
 
@@ -281,6 +295,27 @@ def route_task_session(
         _record_route(result)
         return result
 
+    if required_role == "controller":
+        result = {
+            "task_type": task_type,
+            "required_role": required_role,
+            "active_role": active_role_kind,
+            "active_profile": active_profile,
+            "route_result": ROUTE_WRONG_ROLE,
+            "downstream_allowed": False,
+            "reasons": [
+                WRONG_ROLE_CONTROLLER_MSG,
+                "Controller tasks (process_work_queue / cross-role allocate) "
+                "cannot run in author, reviewer, merger, or reconciler "
+                "worker sessions.",
+            ],
+            "message": WRONG_ROLE_CONTROLLER_MSG,
+            "runtime_switching_supported": runtime_switching_supported,
+            "profile_switch_blocked": not runtime_switching_supported,
+        }
+        _record_route(result)
+        return result
+
     if required_role == "author":
         route = ROUTE_TO_AUTHOR
         message = (