chore: migrate CLAUDE.md to @-import rule structure (custodian integration)

Register with state-hub under custodian domain. Replace monolithic CLAUDE.md
with thin @-import index; distribute content into .claude/rules/ per ops-bridge pattern.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/rules/session-protocol.md

@@ -0,0 +1,48 @@
+## Session Protocol
+
+State Hub: http://127.0.0.1:8000
+
+**Step 1 — Orient**
+```
+get_domain_summary("custodian")
+```
+If offline: `cd ~/the-custodian/state-hub && make api`
+
+**Step 2 — Check inbox**
+```
+get_messages(to_agent="kaizen-agentic", unread_only=True)
+```
+Mark read with `mark_message_read(message_id)`. Reply or act on coordination
+requests before proceeding.
+
+**Step 3 — Scan workplans**
+```bash
+ls workplans/
+```
+For each file with `status: active`, note pending `todo`/`in_progress` tasks.
+
+**Step 4 — Present brief**
+
+1. **Active workstreams** for `custodian` — title, task counts, blocking decisions
+2. **Pending tasks** from `workplans/` + any `[repo:kaizen-agentic]` hub tasks
+3. **Goal guidance** — if `goal_guidance` in summary:
+   - `needs_workplan`: surface as top action — *"Repo goal '{title}' has no workplan yet"*
+   - `alignment_warnings`: flag if active work is not aligned with current goal
+4. **Suggested next action** — highest-priority open item
+5. **SBOM status** — flag if `last_sbom_at` is unset for this repo
+
+If no workstreams: follow First Session Protocol (`first-session.md`).
+
+**During work:** `record_decision()` · `add_progress_event()` · `resolve_decision()`
+
+> State Hub is a *read model*. Bootstrap tools (`create_workstream`, `create_task`)
+> are First Session Protocol only. Work structure belongs in repo files (ADR-001).
+
+**Session close:**
+```
+add_progress_event(summary="...", topic_id="cee7bedf-2b48-46ef-8601-006474f2ad7a", workstream_id="<uuid>")
+```
+If workplan files were modified:
+```bash
+cd ~/the-custodian/state-hub && make fix-consistency REPO=kaizen-agentic
+```