Feature: Status snapshot / readiness report (--markdown)

[Delqhi]

Problem

ECC has ecc status --markdown producing a full readiness report: active sessions, skill health, install health, governance events, blocked work items, exit codes for CI. We have sin-code todo stats (counts only) and sin-code ledger list (sessions only) but no unified status report.

What to do

1. sin-code status --markdown command combining:
   • Active sessions from session.Store (count, titles, ages)
   • Todo readiness from todo.Store (open/blocked/ready/overdue counts)
   • Goal queue from autonomy.Queue (pending/running/verified/failed)
   • Lesson health from lessons.Store (recent failure count)
   • Ledger from ledger.Store (last session verified?)
   • MCP servers from mcpclient (connected/disconnected)
2. --json flag for machine-readable output
3. --exit-code flag: exit 2 when readiness needs attention (CI gate)
4. --write status.md flag to write to file

Acceptance criteria

• sin-code status --markdown produces full report
• --json works
• --exit-code exits 2 on attention needed
• Report covers: sessions, todos, goals, lessons, ledger, MCP

[Delqhi]

Implemented and committed to main.