feat(mcp): doctor-health resource

[radimsem]

Type: AFK

What to build

Read-only MCP resource exposing the health-check report — the same shape remindb doctor --json already produces (overall status header + per-check name/status/detail) — so the desktop client renders the health panel without shelling out to the CLI.

Acceptance criteria

• Resource lists + reads; JSON matches the existing doctor --json schema including the status header
• Reuses the existing pkg/doctor report — no duplicate check logic, read-only (no --fix)
• Follows the feat(mcp): resource infrastructure + overview resource #104 resource contract (passive: no boost, no OpMu, no snapshot)
• skills/remind/SKILL.md updated
• Test asserts schema parity with doctor --json on a fixture (a pass case and a warn case)
• make test green

Blocked by

• feat(mcp): resource infrastructure + overview resource #104