fix: improve issue-lifecycle skill resumption and close-out guidance

[stack72]

Summary

Fixes #42. Three documentation improvements to the issue-lifecycle skill:

• Fix resume command: Replace swamp model get (returns model definition) with swamp data get issue-<N> state-main --json (returns current phase), and add a phase-to-action reference table
• Add in-flight guard: New "Before You Start" section in references/triage.md checks if the issue is already past triage before allowing start — prevents agents from accidentally resetting progress
• Add close-out workflow: New "Closing Out a Shipped Issue" section documents how to mark a shipped issue as done (link_pr → complete)
• Add start safety warning: Blockquote in triage.md clarifying that start unconditionally resets phase to triaging

Test Plan

• deno fmt --check passes
• deno lint passes
• deno run test passes (4236 tests)
• SKILL.md stays under 500 lines (168 lines)
• Verified phase-to-action table matches TRANSITIONS in extensions/models/_lib/schemas.ts

🤖 Generated with Claude Code

[github-actions]

Code Review

Blocking Issues

None.

Suggestions

None — this is a clean documentation improvement.

Verification notes:

• Phase-to-action table matches the Phase enum and TRANSITIONS constant in extensions/models/_lib/schemas.ts (all 7 resumable phases covered; created correctly omitted since it's the pre-start state handled by the triage guard)
• The start reset warning is accurate: TRANSITIONS.start accepts all phases as source, confirming unconditional reset behavior
• The link_pr → complete close-out workflow follows valid transitions (link_pr accepts implementing/pr_open; complete accepts implementing/pr_open)
• Corrected resume command (swamp data get vs swamp model get) returns actual phase data instead of model definition
• SKILL.md stays well under 500-line limit (~169 lines)
• No code changes, no test impact