fix(kanban): tell workers not to use clarify; route to kanban_block instead (#32167)

Kanban workers run headless — no live user is on the other side of `clarify`,
so the call times out (~120s default) and the task sits silently in `running`
with no signal to the operator that input is needed. Reporter observed a real
incident where a worker asked 'promote to production, or check staging first?'
via clarify, the call timed out, the agent hallucinated a fallback, and the
task sat 'running' for hours.

Fix: explicit 'do not call clarify' bullet in two surfaces every kanban worker
sees —

- `agent/prompt_builder.py` KANBAN_GUIDANCE `## Do NOT` section (auto-injected
  into every dispatcher-spawned worker run).
- `skills/devops/kanban-worker/SKILL.md` `## Do NOT` section (the bundled
  worker skill).

Both point at the right pattern: `kanban_comment` (context) + `kanban_block`
(decision needed) — the task surfaces on the board as blocked, the operator
sees it, unblocks with their answer in a comment, and the worker respawns
with the thread.

Co-authored-by: kweiner <17778+kweiner@users.noreply.github.com>

agent/prompt_builder.py

@@ -235,6 +235,11 @@ KANBAN_GUIDANCE = (
     "- Do not shell out to `hermes kanban <verb>` for board operations. Use "
     "the `kanban_*` tools — they work across all terminal backends.\n"
     "- Do not complete a task you didn't actually finish. Block it.\n"
+    "- Do not call `clarify` to ask questions. You are running headless — "
+    "there is no live user to answer. The call will time out and the task "
+    "will sit silently in `running` with no signal to the operator. Instead: "
+    "`kanban_comment` the context, then `kanban_block(reason=...)` so the "
+    "task surfaces on the board as needing input.\n"
     "- Do not assign follow-up work to yourself. Assign it to the right "
     "specialist profile.\n"
     "- Do not call `delegate_task` as a board substitute. `delegate_task` is "