feat: scheduled agent execution via activity-core (WP-0006, v1.3.0)

Enable kaizen agents to run on a regular cadence against a preselected repo
roster, orchestrated by activity-core and prepared by kaizen-agentic — without
this repo owning cron, Temporal workers, or an LLM runtime.

CLI + module:
- src/kaizen_agentic/schedule.py — .kaizen/schedule.yml parse/validate/scaffold
- `kaizen-agentic schedule` group: init, validate, list, prepare <agent>
  (prepare bundles agent prompt + memory + metrics + repo pointers, offline)
- tests/test_schedule_cli.py — 15 tests

Contract & design:
- ADR-005 scheduled agent execution; schema doc + example manifest
- discover_kaizen_scheduled_repos resolver spec, state-hub roster fields,
  kaizen.schedule.prepared event payload, activity-core handoff checklist
- INTEGRATION_PATTERNS Pattern 2 extended with roster model

ActivityDefinition drafts (enabled: false):
- weekly-coach-orientation, weekly-optimization-review

Docs: agency-framework, CLI cheat sheet, PACKAGE_RELEASE runner prereqs,
EcosystemIntegration, CHANGELOG, TODO. Workplan closed (status: done).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- **Scheduled agent execution (WP-0006, ADR-005)** — run agents on a cadence
+  against a preselected repo roster, orchestrated by activity-core and prepared
+  by kaizen-agentic (no Temporal workers or LLM runtime in this repo)
+- **`kaizen-agentic schedule`** CLI group — `init`, `validate`, `list`,
+  `prepare <agent>` (markdown/json) over `.kaizen/schedule.yml`
+- **`.kaizen/schedule.yml`** manifest + schema docs and example
+  (`docs/integrations/schedule-schema.md`, `docs/examples/.kaizen/schedule.yml`)
+- **ActivityDefinition drafts** (`enabled: false`) — `weekly-coach-orientation`,
+  `weekly-optimization-review`
+- **Design specs** — `discover_kaizen_scheduled_repos` resolver, State Hub
+  roster fields, `kaizen.schedule.prepared` event payload, activity-core handoff
+  checklist
+
 ## [1.2.0] - 2026-06-16
 
 ### Added