feat(board): auto-update board Status field on pipeline_stage transitions

[snipcodeit]

Summary

• Add update_board_status shared utility (board-sync.md workflow) that maps pipeline stages to GitHub Projects v2 board Status field options
• Hook board sync into issue.md triage transitions (triaged/needs-info/needs-security-review) and run.md pipeline transitions (executing → verifying → pr-created → done)
• Non-blocking design: board API failures never block pipeline execution (all calls use || true, all error paths return 0)
• Reads field/option IDs from .mgw/board-schema.json or .mgw/project.json at runtime — never hardcodes IDs

Closes #74

Milestone Context

• Milestone: v2 — GitHub Projects Board Management
• Phase: 14 — Pipeline State Sync
• Issue: 4 of 9 in milestone

Changes

• New: .claude/commands/mgw/workflows/board-sync.md — shared update_board_status utility with full data source reference, stage mapping table, and non-blocking contract documentation
• Updated: .claude/commands/mgw/issue.md — board status sync after write_state step (triage transitions: triaged/needs-info/needs-security-review)
• Updated: .claude/commands/mgw/run.md — board status sync at each pipeline checkpoint (executing, discussing, planning, verifying, pr-created, done, blocked); update_board_status function defined in validate_and_load step; board-sync.md added to execution_context
• Updated: .claude/commands/mgw/workflows/state.md — board status sync added to Consumers table

Test Plan

• After triage in issue.md, board item Status updates to matching pipeline_stage option (triaged → Triaged, needs-info → Needs Info, etc.)
• After executor runs in run.md, board item Status updates to Executing
• After PR creation, board item Status updates to PR Created
• After pipeline completes, board item Status updates to Done
• If .mgw/project.json has no node_id (board not configured), all update_board_status calls are silent no-ops — pipeline runs unchanged
• If issue has no board_item_id in project.json (not yet added to board), call is a silent no-op
• If board Status field has no option matching the pipeline stage, call is a silent no-op
• If GraphQL API returns an error, || true suppresses the exit code — pipeline continues