feat(CUST-WP-0001): implement Custodian Agent Runtime bootstrap

T2 complete: OODA loop skeleton with LLM integration, bounded actions,
and 32 offline unit tests.

Deliverables:
- runtime/agent.py     — CLI entry point (--domain/--all/--dry-run/--llm)
- runtime/context.py   — Observe: fetch_state + build_context
- runtime/actions.py   — Act: parse_plan + execute (3 sanctioned writes)
- runtime/README.md    — usage guide and architecture overview
- runtime/tests/       — 32 tests, fully offline
- runtime/pyproject.toml — standalone package with llm-connect dep
- canon/architecture/adr-002-custodian-agent-runtime-design.md

Key design decisions (ADR-002):
- Lives in runtime/ (not a new repo) — tight canon/state-hub coupling
- ClaudeCodeAdapter by default (local-first, no API key)
- Single-pass synchronous OODA for v0.1 simplicity
- Exactly 3 sanctioned write ops: add_progress_event, update_task_status, flag_for_human
- LLM returns JSON block in markdown for structured+auditable output

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

runtime/README.md

@@ -0,0 +1,109 @@
+# Custodian Agent Runtime — v0.1
+
+Single-pass OODA agent loop. Observes project state via the State Hub, reasons
+about it with an LLM, and executes bounded write operations.
+
+## Architecture
+
+```
+agent.py          CLI entry point + OODA orchestrator
+context.py        Observe: fetch state-hub data + build LLM context prompt
+actions.py        Act: execute sanctioned write operations
+prompts/          System prompt templates (future)
+policies/         Agent-level policies (future)
+tool_adapters/    Additional MCP/API tool adapters (future)
+tests/            Unit tests (offline, no live API required)
+```
+
+See `canon/architecture/adr-002-custodian-agent-runtime-design.md` for
+all architectural decisions.
+
+## OODA Loop
+
+```
+Observe  →  fetch_state(domain)           # HTTP GET /state/summary or /state/domain/{slug}
+Orient   →  load_constitution()           # reads canon/constitution/
+             build_context(state, const)  # assembles LLM prompt
+Decide   →  LLM call via llm-connect      # returns markdown + JSON action plan
+Act      →  parse_plan(response)          # extract JSON block
+             execute(plan)                # run sanctioned writes
+```
+
+## Sanctioned Write Operations (ADR-002 D4)
+
+Only three operations may be executed without human approval:
+
+| Operation | State-hub endpoint | Reversible |
+|---|---|---|
+| `add_progress_event` | `POST /progress/` | Yes (append-only log) |
+| `update_task_status` | `PATCH /tasks/{id}/` | Yes |
+| `flag_for_human` | `PATCH /tasks/{id}/` | Yes (clear with `clear_human_flag`) |
+
+## Prerequisites
+
+- State-hub running: `cd state-hub && make api`
+- LLM available: `claude` CLI in PATH (for default `claude-code` provider)
+  or set `OPENROUTER_API_KEY` / `GEMINI_API_KEY` for other providers
+
+## Install
+
+```bash
+cd runtime
+uv sync
+```
+
+## Usage
+
+```bash
+cd runtime
+
+# Focus on custodian domain (cheaper — ~10% of full summary tokens)
+uv run python agent.py --domain custodian
+
+# Full cross-domain view
+uv run python agent.py --all
+
+# Preview actions without executing
+uv run python agent.py --domain custodian --dry-run
+
+# Use a different LLM provider
+uv run python agent.py --domain custodian --llm gemini
+uv run python agent.py --domain custodian --llm openrouter
+
+# Custom state-hub URL
+uv run python agent.py --domain custodian --api-base http://10.0.0.5:8000
+```
+
+## Output
+
+The agent prints a trace to stdout:
+
+```
+[custodian-agent] 2026-03-12T20:00:00 scope=domain=custodian
+[observe] fetching state from state-hub…
+[orient] loading constitution and building context…
+[decide] calling LLM via provider='claude-code'…
+[act] executing plan (live): 1 events, 0 task updates, 0 flags
+  ✓ add_progress_event: 'Reviewed custodian domain: 2 active workstreams…'
+[custodian-agent] done — 1 actions.
+```
+
+The LLM's reasoning trace is saved to `memory/working/agent-session-{ts}-{scope}.md`.
+
+## Tests
+
+```bash
+cd runtime
+uv run pytest -v
+```
+
+All 32 tests run offline (no live state-hub, no LLM API key required).
+
+## Extending
+
+- **New observations**: extend `build_context()` in `context.py`
+- **New actions**: add to `actions.py` and update `SANCTIONED_ACTIONS` — but
+  any expansion of the action surface requires a new ADR and human approval
+  (see constitution §2–§4)
+- **Tool adapters**: add to `tool_adapters/` following the llm-connect
+  `LLMAdapter` pattern