[Maintainer] Upgrade to v0.19.6

[github-actions]

[Maintainer] Upgrade to v0.19.6

Current version: 0.19.4
Target version: 0.19.6

Upgrade Notes

Wires the fleet registry into the admin dashboard end-to-end so that
production deployments at https://caretaker.cat-herding.net light up
with real heartbeat, alert, webhook, and doctor data. Closes the gap
where every child repo in docs/fleet.yml was effectively invisible to
the admin UI even when it ran caretaker on schedule.

Added

• Persistent SQLiteFleetRegistryStore (src/caretaker/fleet/sqlite_store.py)
  — SQLite-backed implementation of the registry with the same async API
  as the in-memory store. Keeps the most recent 32 heartbeats per repo
  in a fleet_heartbeats ring buffer plus the latest snapshot in
  fleet_clients. Activated by setting CARETAKER_FLEET_DB_PATH
  (default location ~/.local/state/caretaker/fleet-registry.db); the
  legacy in-memory store remains the default to avoid surprising tests.
  Survives backend restarts so dashboard data no longer evaporates on
  every pod recycle.
• fleet_registry block in setup-templates/templates/config-default.yml
  — opt-in template (enabled: false) that points at the production
  endpoint with HMAC and timeout pre-wired. Includes a 22-line comment
  block explaining the contract.
• CARETAKER_FLEET_SECRET env wiring in setup-templates/templates/workflows/maintainer.yml
  — exported in all three env: blocks (bootstrap-check, run, and
  self-heal-on-failure). Indentation across the workflow normalised to
  2-space nesting at the same time.
• Step 2.8 in setup-templates/SETUP_AGENT.md — guides Copilot
  through enabling the fleet registry on each child repo (config edit
  • secret + verification command).
• docs/fleet-opt-in-runbook.md — operator-facing runbook
  enumerating the 12 child repos in docs/fleet.yml with per-repo
  caveats and a four-step opt-in checklist.
• caretaker fleet status CLI command — local config inspector;
  prints the resolved fleet_registry block and notes whether the
  signing secret is populated.
• caretaker fleet register-self CLI command — sends one
  signed heartbeat to verify a repo's registration round-trip;
  echoes the dashboard's HTTP response for fast diagnosis.
• Frontend Alerts page (/alerts) — consumes
  /api/admin/fleet/alerts with an "open only" toggle, severity
  badges, and links back to per-repo detail. Closes the dead link
  from AlertsBanner.tsx.
• Frontend FleetDetail page (/fleet/:owner/:repo) — per-repo
  drill-down with the last 32 heartbeats, enabled-agent pills, and
  goal-health/error trends. Reachable from any row of the Fleet page.
• FleetClient, FleetClientDetail, FleetAlert,
  FleetAlertList types — added to frontend/src/lib/types.ts so
  TypeScript builds no longer rely on an implicit FleetAlert import.

Changed

• GET /api/admin/fleet/{owner}/{repo} — now accepts
  ?include_history=true&history_limit=N (max 32) and returns the
  per-repo heartbeat ring buffer alongside the client snapshot. Used
  by the new Fleet detail page.
• fleet/store.py get_store() — picks SQLite backing when
  CARETAKER_FLEET_DB_PATH is set; otherwise keeps the in-memory
  default. reset_store_for_tests(store=None) accepts an explicit
  store override for SQLite test fixtures.
• fleet/__init__.py — re-exports SQLiteFleetRegistryStore,
  resolve_db_path, and DEFAULT_DB_PATH_ENV.
• docs/fleet-registry.md — example endpoint replaced with the
  production URL https://caretaker.cat-herding.net/api/fleet/heartbeat;
  persistence section rewritten to describe the new SQLite seam.

Fixed

• Dead admin routers wired into the FastAPI app
  (src/caretaker/mcp_backend/main.py):
  • caretaker.admin.health_api — GET /health/doctor now reachable;
    configured with the live admin_data, optional graph store, and
    fleet store on lifespan.
  • caretaker.admin.webhooks_api — GET /api/admin/webhooks/deliveries
    now reachable, and the github_webhook handler calls
    register_delivery() after each ack so the dashboard can show
    delivery history.
• Frontend /alerts 404 — AlertsBanner.tsx linked to a route
  that did not exist; the new Alerts page closes that gap.
• Workflow YAML indentation — setup-templates/templates/workflows/maintainer.yml
  had inconsistent 7/9-space indentation on three - name: step
  headers and their env: maps. Normalised to 2-space nesting; YAML
  now parses cleanly without GitHub Actions' lenient mode.

📋 Full Changelog

@copilot Please apply this upgrade.
See .github/agents/maintainer-upgrade.md for instructions.

FROM: 0.19.4
TO: 0.19.6
BREAKING: False

Steps:

1. Update version pins in pyproject.toml / requirements.txt
2. Update any workflow references
3. Run tests to verify compatibility
4. Update the version in config if applicable

Acceptance criteria:

• Version updated to target
• All tests pass
• No regressions