feat: Player2 Kanban Transformation & Architectural Reinforcement

[Tristan578]

feat: Player2 Kanban Transformation & Architectural Reinforcement

This PR transforms the taskboard project into Player2 Kanban, an agent-native, professional-grade task management system. It introduces a robust bridge between local "vibe coding" environments and production GitHub workflows.

🚀 Key Features

1. Bidirectional GitHub Sync Engine

• HTML-Comment Metadata: Replaced fragile YAML frontmatter with hidden Base64-encoded JSON inside HTML comments at the bottom of Issue bodies. This ensures metadata (User Stories, ACs, LexoRank) is indestructible to human edits on GitHub.
• Background Sync Queue: Implemented a persistent SQLite-backed queue (sync_jobs) and a background worker. Sync actions are now non-blocking and safe from GitHub secondary rate limits.
• Asynchronous Git Hooks: Updated the pre-push and post-merge hooks to trigger fire-and-forget syncs, ensuring your terminal never hangs during a push.

2. "Strict Mode" & Quality Enforcement

• Professional Standards: When a project is in Strict Mode, the system enforces the presence of a User Story and Acceptance Criteria (Gherkin).
• Hard API Blocking: Both agents (via API) and humans (via UI) are blocked from creating "ready" tickets without full specs.
• Draft Mode: Added a "Draft" status that allows users to quickly jot down notes/bugs in Strict projects without bypass validation. Drafts remain local and are never pushed to GitHub until "Published".

3. Multiplayer Determinism (LexoRank)

• Deterministic Card Order: Implemented string-based LexoRank positioning. Ticket order is now synced to GitHub, ensuring every developer on the team sees the exact same board layout.

4. Tombstone Deletions

• Soft Deletes: Deleting a ticket locally now creates a "tombstone". The Sync Engine closes the corresponding GitHub issue and then purges the local record, preventing "zombie" tickets.

5. Multi-Agent Skill Suite

• Tailored Instructions: Added the player2-kanban agent-config install command to inject official standards for Cursor, Claude, Gemini, Windsurf, Antigravity, and GitHub Copilot.

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🧪 Testing Instructions

Backend (Go)

1. Prerequisites: Ensure you have a GITHUB_TOKEN set in your environment.
2. Run Tests: go test ./internal/db/... ./internal/server/... ./internal/github/...
3. Manual Verification:
   • Link a project: player2-kanban project link <id> <repo_url>
   • Create a Draft: Verify it appears on the board but NOT on GitHub.
   • Publish Ticket: Move the draft to "Todo" and verify the GitHub Issue is created with the hidden metadata comment.
   • Move Ticket: Move a card on the board and verify the LexoRank metadata is updated on GitHub.

Frontend (React)

1. Build: cd web && npm install && npm run build
2. Verify UI:
   • Check for the "Draft" badge on cards.
   • Verify red border validation in CreateTicketModal when in Strict Mode.
   • Use the "Publish Ticket" button in the TicketPanel.

📦 Documentation Updates

• Updated README.md with rebranding and new setup instructions.
• Updated CONTRIBUTING.md with proper attribution to the upstream tcarac/taskboard.