Restate the comment standard as numbered voice rules

[Kevinjohn]

Part of #1406 (T5). Merge predecessor: none.

• DEFENSIVE-CODING.md §7 is restated as eleven numbered comment rules. Every earlier requirement is kept (TSDoc on exports, why-comments, guard and catch comments, head paragraphs, current contract over history), and voice rules are added: no CAPS emphasis, no em-dashes, no ticket references, no banners, no commented-out code, TODO only with an issue URL.
• AGENTS.md points at §7 for comment voice.
• No source comments change here; the tree-wide sweep and checker are a later task.

Validation: integrated with the other Batch 1 branches on b04a75f5 (merge of origin/main da72918): pnpm run format:check, pnpm run docs:build (no drift) and pnpm run gate:server pass on Node 24.16.0. Independently reviewed before opening.

Merge order

1. Route support to Discussions and remove PR screenshots #1411, Add project status, comparison, testing and philosophy pages #1412, Archive changelog sections before 0.41.0-alpha.3 #1414 (independent)
2. Add a first-change path for contributors #1413 (after Archive changelog sections before 0.41.0-alpha.3 #1414), Restate the comment standard as numbered voice rules #1415, Reduce configuration and hide password MFA #1416
3. Rename SMALLSASS_ACCOUNT_ settings to CAPACITYLENS_ #1417 → Add an init command that writes the environment file #1418
4. Retire unused settings and derive engagement grouping #1419 → Move diagnostics to an Owner and Admin page #1420 → Reshape the documentation into four role guides #1421 → Use @/ for app imports that leave their folder #1422 → Consolidate server test scaffolding #1423 → Normalise server route handlers and reply messages #1424 → Apply the comment-voice rules and check them in the gate #1425 (Apply the comment-voice rules and check them in the gate #1425 also after Restate the comment standard as numbered voice rules #1415) → Name the tenant boundary account in code #1426

Merge predecessor for this PR: none.

[Kevinjohn]

Polish review: no P1/P2 findings.

• format:check and the documentation tests pass.
• No conflict with Apply the comment-voice rules and check them in the gate #1425, the comment sweep that applies these rules.

Merge order for this batch: #1411, #1412, #1414 → #1413, #1415, #1416 → #1417 → #1418, #1419 → #1420 → #1421 → #1422 → #1423 → #1424 → #1425 → #1426. Predecessor: none.