feat(gateway): carry intake technical depth down the chain + widen review coherence scope (#491)

Two structural issues flagged by the CEO:

1. Task technical-depth dilution — intake's rich analysis (file:line
   targets, code examples, rationale) was getting lost as it traveled
   umbrella -> root-subtask -> cell -> dev. The detail IS preserved in
   Task.description; the dilution was in delegation (PMs re-authoring)
   and the intake prompt not demanding depth.

   Fixes:
   - evidence_repo: ancestor_context_for_task walks the parent chain
     (cycle-guarded, depth-capped 16, desc-clipped 1500) and surfaces it
     as parent_context in the evidence payload, so a leaf dev finally
     sees the upstream intake analysis instead of a bare title.
   - evidence_builder: Task.description now rides in the payload;
     EvidencePayload gains description + parent_context (omit-when-empty
     so no null noise).
   - orchestrator: _description_body (capped 4000) injects the
     description into the dev spawn prompt + SessionStart briefing.
   - role prompts (main_pm/cell_pm/developer/prompter): teach pass-the-
     torch, don't-dim-it; prompter now demands file:line/code-examples
     in the_work/notes (reconciled with the no-code-level-ACs-on-roots
     rule). main_pm's brief-not-a-spec scoped: not-a-spec applies to the
     solution only, facts forward verbatim.

2. PR-review/QA scope too narrow — they only checked the AC checklist,
   not whether the change is coherent with project structure/intent.

   Fixes:
   - qa.md + pr_reviewer.md: Coherence & intent rule (intent via
     description+parent_context, coherence with project patterns,
     standards). Criterion-less major findings allowed for intent drift
     (Finding.criterion is optional).
   - parent_context + description wired into the gate/QA/inbound-PR
     evidence builders (fail-open, logged).

Skipped per YAGNI: a technical_spec JSONB column (detail is already in
description) and a criterion_kind enum (criterion is already optional).

All gates green: ruff, mypy (1152), pytest (12883 passed, 94.82% cov),
xenon, vulture, bandit, pip-audit, deptry, alembic, import-linter,
foundation-check.

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

tests/unit/gateway/test_evidence_populates_files_changed.py

@@ -141,7 +141,9 @@ async def test_evidence_populates_journal_highlights() -> None:
     env = await ca.evidence(agent_id=agent_id, task_id=task_id)
     body = env.as_dict()
     assert body["evidence"]["journal_highlights"] == highlights
-    evidence_repo.journal_highlights_for_task.assert_awaited_once_with(task_id)
+    evidence_repo.journal_highlights_for_task.assert_awaited_once_with(
+        task_id, include_ancestors=True
+    )
 
 
 @pytest.mark.asyncio