fix(kanban): suppress dispatcher stuck-warn when ready queue holds only non-spawnable assignees

After PR #20105 (dispatcher skips ready tasks whose assignee fails
``profile_exists()`` to prevent the orion-cc/orion-research crash
loop), the gateway and CLI emit a spurious "kanban dispatcher stuck:
ready queue non-empty for N consecutive ticks but 0 workers spawned"
warning every 5 minutes on multi-lane setups where the queue is
steadily full of human-pulled work assigned to terminal lanes.

The warn is intended to catch real failure modes (broken PATH,
missing venv, credential loss for a real Hermes profile). On a
multi-lane host it fires forever even though everything is healthy:
the dispatcher correctly chose not to spawn, and there is nothing
for the operator to fix.

Changes:

* ``DispatchResult`` gains a ``skipped_nonspawnable`` field
  (separate from ``skipped_unassigned``) so callers can distinguish
  "task missing an owner — operator should route it" from "task
  owned by a control-plane lane — terminal will pull it".
* ``dispatch_once`` routes the ``not profile_exists(assignee)`` skip
  into the new bucket (was lumped into ``skipped_unassigned``).
* New helper ``has_spawnable_ready(conn)`` returns True iff at least
  one ready+assigned+unclaimed task in the DB has an assignee that
  maps to a real Hermes profile. Falls back to legacy "any
  ready+assigned" when ``profile_exists`` is unimportable so degraded
  installs still surface the original warn.
* The gateway dispatcher (``gateway/run.py``) and the CLI standalone
  daemon (``hermes_cli/kanban.py``) both swap their cheap
  ``ready_nonempty`` probe to use ``has_spawnable_ready``. Stuck-warn
  now fires only when there is genuine spawnable work the dispatcher
  failed to start.
* CLI dispatch output prints ``Skipped (non-spawnable assignee —
  terminal lane, OK)`` for visibility without alarm.

Tests:

* New ``has_spawnable_ready`` cases (empty queue, terminal-lane
  only, mixed real+terminal).
* New ``test_dispatch_skips_nonspawnable_into_separate_bucket``
  verifies the bucketing change.
* Updated ``test_dispatch_skips_unassigned`` to assert no
  cross-leak.
* Added ``all_assignees_spawnable`` fixture in
  ``tests/hermes_cli/conftest.py`` and threaded it through dispatcher
  tests that use synthetic assignees ("alice", "bob"). PR #20105
  (the parent commit) silently broke 8 such tests by routing those
  assignees into ``skipped_nonspawnable`` instead of spawning; this
  PR repairs them as part of the same code area.

Verified locally: 246/246 kanban-suite tests pass.

Stacks on top of fix/kanban-dispatcher-skip-missing-profile-2026-05-05
(PR #20105). Reviewer: this PR is meant to merge AFTER #20105.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

gateway/run.py

@@ -3906,7 +3906,17 @@ class GatewayRunner:
             return out
 
         def _ready_nonempty() -> bool:
-            """Cheap probe: is there a ready+assigned+unclaimed task on ANY board?"""
+            """Cheap probe: is there at least one ready+assigned+unclaimed
+            task on ANY board whose assignee maps to a real Hermes profile
+            (i.e. one the dispatcher would actually spawn for)?
+
+            Tasks assigned to control-plane lanes (e.g. ``orion-cc``,
+            ``orion-research``) are pulled by terminals via
+            ``claim_task`` directly and never spawnable, so a queue full
+            of those is "correctly idle", not "stuck". Filtering them out
+            here keeps the stuck-warn fire only on real failures (broken
+            PATH, missing venv, credential loss for a real Hermes profile).
+            """
             try:
                 boards = _kb.list_boards(include_archived=False)
             except Exception:
@@ -3916,12 +3926,7 @@ class GatewayRunner:
                 conn = None
                 try:
                     conn = _kb.connect(board=slug)
-                    row = conn.execute(
-                        "SELECT 1 FROM tasks "
-                        "WHERE status = 'ready' AND assignee IS NOT NULL "
-                        "    AND claim_lock IS NULL LIMIT 1"
-                    ).fetchone()
-                    if row is not None:
+                    if _kb.has_spawnable_ready(conn):
                         return True
                 except Exception:
                     continue