feat(memory): add memory CLI command group and project memory ADRs

- Add docs/adr/ADR-001-workplan-convention.md (formalises existing convention)
- Add docs/adr/ADR-002-project-memory-convention.md (file location, structure,
  session protocols, opt-out, CLI interface)
- Implement `kaizen-agentic memory` command group: show, init, brief, clear
  - Memory stored at .kaizen/agents/<name>/memory.md in project root
  - `init` scaffolds the standard memory template with YAML frontmatter
  - `brief` lists all agent memories + note that coach synthesis is pending T13
  - `clear` deletes with confirmation prompt

WP-0002 T07 and T08 done.

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

docs/adr/ADR-001-workplan-convention.md

@@ -0,0 +1,57 @@
+---
+id: ADR-001
+title: Workplan Convention
+status: accepted
+date: "2026-03-18"
+---
+
+# ADR-001 — Workplan Convention
+
+## Status
+
+Accepted
+
+## Context
+
+kaizen-agentic needs a way to track planned work that is version-controlled,
+visible to the state-hub, and authoritative when the two diverge.
+
+## Decision
+
+Work items originate as Markdown files in `workplans/` **before** being
+registered in the state-hub DB. The file is always authoritative; the DB is
+a read/query model derived from it.
+
+**File naming:** `workplans/kaizen-agentic-WP-NNNN-<slug>.md`
+**ID prefix:** `KAIZEN-WP`
+
+### Required YAML frontmatter
+
+```yaml
+---
+id: KAIZEN-WP-NNNN
+type: workplan
+title: "..."
+domain: custodian
+repo: kaizen-agentic
+status: active | completed | archived
+owner: kaizen-agentic
+topic_slug: custodian
+state_hub_workstream_id: <uuid>
+created: "YYYY-MM-DD"
+updated: "YYYY-MM-DD"
+---
+```
+
+### Task tracking
+
+Tasks use `- [ ]` / `- [x]` checkboxes with a `T##` code prefix. A
+`## State Hub Task IDs` table at the end of each workplan maps codes to
+DB UUIDs so status can be synced without a list_tasks lookup.
+
+## Consequences
+
+- File is the source of truth; DB drift is auto-fixable via
+  `check_repo_consistency(fix=True)`.
+- Tasks must be created in the file first, then registered in the hub.
+- C-12 warnings are expected when the DB host has not yet seen local changes.