docs(rag): add prompter/secretary role docs + refresh guardrails surface

The agents' runtime KB had drifted three releases behind the gateway. Add the
two missing role docs (prompter, secretary — both live-session SDK chat roles,
human-only) and fold the AC/decomposition guardrails and per-dev code queues
into the high-traffic PM docs:

- task-model: acceptance_criteria_ids + parent_ac_refs fields and how the
  child->parent AC link works.
- task-planning: covers_parent_criteria on delegate, the parent_ac_coverage /
  unclaimed_parent_acs briefing fields, the decomposition-floor and roll-up
  gates (safe-by-construction), and per-dev sequenced code queues.
- task-tools: same coverage note + correct stale verbs — QA is
  pass_review/fail_review (not pass/fail), cell_pm gains reassign, and main_pm
  no longer claims submit_up/reassign it does not have.

docs/rag/architecture/task-model.md

@@ -8,10 +8,26 @@
 | `title` | String | Task title |
 | `description` | Text | Detailed description |
 | `acceptance_criteria` | Array | How we know it's done |
+| `acceptance_criteria_ids` | Array | Stable per-criterion id (1:1 with `acceptance_criteria`) |
+| `parent_ac_refs` | Array | Parent AC ids this subtask is responsible for |
 | `status` | Enum | Lifecycle state |
 | `priority` | Int | 0=P0 (highest) to 3=P3 |
 | `team` | Enum | backend, frontend, ux_ui |
 
+## Acceptance-Criteria Tracking
+
+Every task's `acceptance_criteria` get a parallel list of stable
+`acceptance_criteria_ids` — one id per criterion, generated automatically when a
+task is created. The ids are stable across edits, so other tasks can reference a
+specific criterion.
+
+When a parent task is decomposed, each subtask declares which parent criteria it
+covers in `parent_ac_refs` (set from the `covers_parent_criteria` argument to
+`delegate`). That child→parent link is what lets the org guarantee a
+decomposition actually covers the parent's full intent. See
+`docs/rag/workflows/task-planning.md` for the coverage gates and the PM's
+coverage briefing.
+
 ## Task Types
 
 | Type | Description |