docs(0.7.0): document Grok provider, self-heal, PR-reviewer across the RAG + how-to docs

Close the doc gaps the audit found in the agent knowledge base and the human
walkthrough:
- config-reference: add the Grok provider env table (host ~/.grok subscription
  mount, grok-build, idle-kill, cost cap) and the Self-Healing CI loop toggles.
- agent-model: provider-aware Model Configuration (ANTHROPIC default / GROK) +
  add the pr_reviewer / prompter / secretary roles to the Roles table.
- tool-permissions: 'three' -> five MCP servers (roboco-optimal, roboco-docs) +
  PR Reviewer / Prompter / Secretary tool sections.
- new roles/pr-reviewer.md (the 22nd agent had no role doc); permissions +
  agent-uuids + task-tools 'PR Reviewer flow' all gain the role.
- api-endpoints: drop the removed USAGE_UPDATE event (only USAGE_SNAPSHOT exists).
- how-to: self-healing CI loop + Company Scorecard (ch.5), inbound external-PR
  review + CEO Supersede/Dismiss queue (ch.4).

Every claim verified against current code by the audit (grok model grok-build,
auth ~/.grok, no metered API; opencode fully removed).

docs/rag/architecture/agent-uuids.md

@@ -64,6 +64,9 @@ delegate(assigned_to="00000000-0000-0000-0001-000000000001", ...)
 | `product-owner` | `00000000-0000-0000-0004-000000000002` |
 | `head-marketing` | `00000000-0000-0000-0004-000000000003` |
 | `auditor` | `00000000-0000-0000-0004-000000000004` |
+| `intake-1` (prompter) | `00000000-0000-0000-0004-000000000005` |
+| `secretary-1` | `00000000-0000-0000-0004-000000000006` |
+| `pr-reviewer-1` | `00000000-0000-0000-0004-000000000007` |
 
 ## CEO (0000)