docs: align kanban readiness docs and smoke tests

Salvages #28199 by @bensargotest-sys. Aligns Kanban docs with current
tool registration: dispatcher-spawned task workers get task tools,
profiles that explicitly enable the kanban toolset get orchestrator
routing tools (kanban_list, kanban_unblock). Corrects failure-limit
text to current default of 2. Hardens the e2e subprocess script to
resolve repo root and use the spawnable default assignee. Updates the
diagnostics severity fixture to assert error below the critical
threshold.

AGENTS.md

@@ -830,10 +830,11 @@ kanban task.
   `unlink`, `comment`, `complete`, `block`, `unblock`, `archive`,
   `tail`, plus less-commonly-used `watch`, `stats`, `runs`, `log`,
   `assignees`, `heartbeat`, `notify-*`, `dispatch`, `daemon`, `gc`.
-- **Worker toolset:** `tools/kanban_tools.py` exposes `kanban_show`,
-  `kanban_complete`, `kanban_block`, `kanban_heartbeat`, `kanban_comment`,
-  `kanban_create`, `kanban_link` — gated by `HERMES_KANBAN_TASK` so
-  the schema only appears for processes actually running as a worker.
+- **Worker/orchestrator toolset:** `tools/kanban_tools.py` exposes
+  `kanban_show`, `kanban_complete`, `kanban_block`, `kanban_heartbeat`,
+  `kanban_comment`, `kanban_create`, `kanban_link`; profiles that
+  explicitly enable the `kanban` toolset outside a dispatcher-spawned
+  task also get `kanban_list` and `kanban_unblock` for board routing.
 - **Dispatcher:** long-lived loop that (default every 60s) reclaims
   stale claims, promotes ready tasks, atomically claims, and spawns
   assigned profiles. Runs **inside the gateway** by default via
@@ -849,8 +850,9 @@ Isolation model:
 - **Tenant** is a soft namespace *within* a board — one specialist
   fleet can serve multiple businesses with workspace-path + memory-key
   isolation.
-- After ~5 consecutive spawn failures on the same task the dispatcher
-  auto-blocks it to prevent spin loops.
+- After `kanban.failure_limit` consecutive non-success attempts on the
+  same task (default: 2), the dispatcher auto-blocks it to prevent spin
+  loops.
 
 Full user-facing docs: `website/docs/user-guide/features/kanban.md`.