docs: add project manifest

[shtse8]

Summary

• add PROJECT.md with repo goal, lifecycle, boundary, public surfaces, and delivery notes
• add .doctrine/project.json for central doctrine audit
• add AGENTS.md pointer to repo-local manifest and SylphxAI/doctrine

Validation

• python3 -m json.tool .doctrine/project.json
• python3 -m json.tool package.json
• Ruby YAML parse for action.yml, detect/action.yml, workflows, and examples
• git diff --check
• doctrine project-control-plane-audit.py --repo SylphxAI/bump --ref codex/project-manifest-bump --fail-on-drift --json => PRESENT

Notes

• Documentation-only; no CLI/action/package/CI/release behavior changed.
• GitHub push surfaced an existing default-branch Dependabot alert; not introduced by this PR.

[shtse8]

CI status update from doctrine rollout:

• The project-control manifest itself audits PRESENT on this PR head.
• CI fails on existing Biome lint/format diagnostics in source/test files, not on the new PROJECT.md, .doctrine/project.json, or AGENTS.md files.
• Latest failed run: https://github.com/SylphxAI/bump/actions/runs/27913443327, job test, step Lint.
• Follow-up issue: Fix existing Biome lint debt blocking documentation-only PRs #71

I am leaving this PR open rather than bypassing branch protection or mixing broad source lint cleanup into the manifest rollout.

[shtse8]

Superseded by #73. This branch has unrelated history against current main and carries stale workflow/doc diffs; #73 is the clean main-based ADR-81 selector/package-release replacement with remote audit/projection proof.

[shtse8]

Closing in favor of #73, the clean replacement PR.