R6: Public repo polish — templates, description, topics, visibility flip

[jmcte]

Goal

Final pass on the public-facing repo metadata so the project signals "maintained" the moment it goes public, and so newcomers have the right entry points (issue templates, contribution flow, contact).

This is R6 of six release milestones (R1–R6) leading to v0.1.0. Should be the last milestone closed, immediately before the visibility flip and tagging v0.1.0.

Evidence

• project.bootstrap.yaml:35-38 — templates.issueTemplates declares bug and feature. Verify they exist on disk under .github/ISSUE_TEMPLATE/.
• project.bootstrap.yaml:34 — templates.pullRequest: standard. Verify a PR template exists.
• project.bootstrap.yaml:6 — visibility: public in the manifest, but the bootstrap tool may not have flipped the actual repo visibility yet (current GitHub state shows "visibility":"public" per recent API check, so confirm).
• CODEOWNERS — currently 9 bytes, sufficient but worth verifying it actually matches the manifest's codeowners.pattern: "*" → @jmcte rule.

Acceptance criteria

Templates

• .github/ISSUE_TEMPLATE/bug.yml exists with a structured form: reproduction steps, expected/actual, mpi --version, mpi doctor output, OS, fixture-mode-only or live-adapter mode.
• .github/ISSUE_TEMPLATE/feature.yml exists with: motivation, alternatives considered, scope (v0.1 / Phase 2 / out-of-scope).
• .github/ISSUE_TEMPLATE/config.yml points the "Security vulnerability" link to SECURITY.md and disables blank issues.
• .github/PULL_REQUEST_TEMPLATE.md exists with: summary, scope (which R# milestone), test plan, doc updates checklist, fixture changes checklist.

Repo metadata

• GitHub repo "About" — short description (e.g. "Intelligence layer for email — metadata index + reviewed semantic extraction over MailPlus").
• GitHub repo topics: mailplus, email, python, metadata-index, semantic-extraction, synology (or whichever subset matches).
• Verify website link points at the README anchor or repo root (no broken external URL).
• Verify CODEOWNERS matches the manifest and protects all paths.

Contribution surface

• CONTRIBUTING.md has a "good first issue" section pointing at the repo's good first issue label query.
• Confirm the release-v0.1 label exists, plus baseline labels: bug, feature, documentation, epic, good first issue, help wanted.

Visibility flip checklist (gate at the very end)

• R1, R2, R3, R4, R5 all closed.
• bash scripts/ci/run-fast-checks.sh green on main.
• mpi doctor green on a fresh clone with pip install.
• If repo is still private (verify), flip to public.
• Tag v0.1.0 (handled by R5 workflow once tagged).

(Optional) Code of conduct

• Decide whether to add CODE_OF_CONDUCT.md. If yes, use the Contributor Covenant 2.1 template; if no, document the decision in this issue and close.

Definition of done

• Repo is public, has v0.1.0 tagged, has a populated GitHub Release, and has functional issue/PR templates wired up.
• Following R6 there should be no more release-blocking issues open with the release-v0.1 label.