chore: align server, shared, and script comments

[Kevinjohn]

Closes #1468

Aligns TSDoc and source comments in server/, shared/, and scripts/ with DEFENSIVE-CODING.md section 7. Removes stale history and adds contract documentation while preserving authorization, tenancy, migration, audit, recovery, and validation behavior. The accepted-syntax notes in scripts/check-comment-voice.mjs remain because they describe checker inputs. The @vite-ignore directive remains inline because the dynamic import requires it.

The shared entity allocation note requested by #1467 is removed here; #1467 must merge after this PR. Redundant test comments were removed where they only repeated adjacent assertions. The required TSDoc puts server/src/routes/entityRoutes.ts two lines over its ceiling, so its existing ratchet policy records a temporary 402-line baseline for a future module split.

Validation:

• Pre-push checks: Prettier, typecheck, lint, and file-size policy
• Comment-style checker across 1,301 source files
• git diff --check

No application test suites were run because this change only edits comments.

Merge predecessor: none. #1467 must merge after this PR.

Merge order

#1472 → #1473, #1474, #1466

• Set body text to 13px #1465 and chore: align repository configuration comments #1471 have merged. No textual conflicts with main (2950329) or between any pair of the remaining PRs. All four merged in this order onto main cleanly, and the combined tree passes format, typecheck, lint and the docs build (tree clean).
• Rewrite the documentation front door around four role quick starts #1466 lands last because it carries regenerated docs/ output.
• Each PR will be behind main once its predecessor lands; update the branch from main before merging.

Merge predecessor for this PR: none.

Conflicts: none.

[Kevinjohn]

Polish review: no P1 or P2 findings, no changes pushed.

• Comment-only claim verified by comparing comment-stripped printed ASTs of every changed source file against main. The only differences are one renamed test title in shared/src/lib/integrity.test.ts (assertions unchanged; file passes, 40 tests) and the new server/src/routes/entityRoutes.ts baseline in scripts/file-size-exceptions.json, which the file-size policy accepts.
• Ladder passed on Node 24 at the PR head: pnpm run check:push (format, typecheck, lint with zero warnings, file-size policy) and pnpm run policy:comment-voice.
• Integration: chore: align repository configuration comments #1471, chore: align server, shared, and script comments #1472, fix: surface unexpected repeat time-off failures #1473, chore: clarify E2E test comments #1474 and Rewrite the documentation front door around four role quick starts #1466 merged in that order onto main at 8141c39 without conflicts; check:push, policy:comment-voice, docs:build (tree clean afterwards) and the documentation, runbook and user-story suites (430 tests) pass on the combined tree.

Merge predecessor: none. #1473 follows this PR.