Publish contributor roadmap and workflow

[CoderSufiyan]

Summary

• add a versioned roadmap covering all 38 implementation issues from v0.5.0 through v1.1.0
• replace stale contribution guidance with issue claiming, dependency, fixture, static-verification, runtime-consent, and PR requirements
• add feature and bug issue forms, private vulnerability reporting, and a pull request template
• link the README to the public roadmap and Project board

GitHub setup

• create seven release milestones and assign every implementation issue
• add roadmap, version, area, ready, and blocked labels
• repair the Extend GitHub Action with policy and baseline inputs #34, Add attest command for verified MCP artifacts #23, Add offline verification mode #30, and Add verification baseline support #45 dependency graph
• create and populate the public 38-item Project board
• create and pin roadmap announcement [Roadmap] Version plan and contribution guide #68
• enable private vulnerability reporting

Verification

• bun run test (36 tests)
• bun run build
• issue-template YAML validation
• git diff --check