feat: auto-assign issue to current user during lifecycle start

[stack72]

Summary

• Wire auto-assignment into the start() method of the @swamp/issue-lifecycle extension model
• When triage begins, reads the current user's username from local auth (~/.config/swamp/auth.json), resolves it to a userId via the eligible-assignees endpoint, and PATCHes the issue's assignees additively
• All assignment failures are best-effort warnings — the triage flow never breaks
• Bumps model version to 2026.04.12.1

Changes

• extensions/models/_lib/swamp_club.ts: Export loadAuthFile (now returns optional username); add fetchEligibleAssignees(), resolveUserId(), updateAssignees() to SwampClubClient; extend FetchedIssue with assignees field
• extensions/models/issue_lifecycle.ts: Wire assignment block into start() after context/state writes; add version upgrade entry
• extensions/models/issue_lifecycle_test.ts: 6 new unit tests with fetch stub infrastructure covering happy path, additive merge, idempotent, missing username, 403 on lookup, PATCH failure
• extensions/models/README.md: Update start description in methods table
• .claude/skills/issue-lifecycle/references/triage.md: Add auto-assignment documentation section

Test Plan

• All 28 extension model tests pass (6 new + 22 existing)
• Full test suite: 4292 passed, 0 failed
• deno check — clean
• deno lint — clean
• deno fmt — clean
• deno run compile — binary built
• Changes synced to systeminit/swamp-extensions and systeminit/swamp-club

Closes swamp-club#86

🤖 Generated with Claude Code

[github-actions]

Code Review

Blocking Issues

None.

Suggestions

1. Double loadAuthFile() call (issue_lifecycle.ts:493): During start(), loadAuthFile() is called twice — once internally by createSwampClubClient() (for apiKey/serverUrl) and once directly by start() (for username). A future cleanup could have createSwampClubClient return the username alongside the client, or have the client store it. Not blocking since it's a minor I/O redundancy on a local file.

Notes

• DDD: SwampClubClient is the right home for fetchEligibleAssignees/resolveUserId/updateAssignees — it stays within its infrastructure service responsibility. EligibleAssignee is a clean value object. The orchestration in start() keeps assignment as a best-effort side effect after the core lifecycle transition, which is the correct application-layer pattern.
• CLAUDE.md compliance: No any types, all promises awaited, AbortSignal.timeout on every outbound call, license headers present, named exports used. No libswamp import boundary violations (extensions don't import from src/libswamp).
• Test coverage: 6 new tests cover the key paths well — happy path, additive merge, idempotency, missing username, 403 on lookup, and PATCH failure. The fetch stub infrastructure is clean and reusable.
• Security: API key stays in the private #apiKey field, auth file is read from the well-known XDG/HOME config path, no user input is interpolated into sensitive contexts.