Comment & JSDoc cleanup (maintainer task)

Session notes under docs/phases/temp/ are gitignored; this file is a tracked checklist you can link from PRs.

Goal

Reduce noise and keep documentation where it earns its keep:

1. Remove redundant line-by-line comments and JSDoc that only restate the identifier or repeat obvious TypeScript types.
2. Keep short comments at unstable or non-obvious boundaries: workarounds, invariants, perf traps, security, or places contributors change often (config keys, CLI flags, public API surfaces).
3. Prefer one block for a group of related constants (e.g. a single JSDoc above an export const object or a /** … */ block covering a small enum-like group) instead of repeating /** … */ on every line unless a single value needs a distinct note.
4. Rich JSDoc for public or frequently imported functions: parameters, return value, thrown errors, and one link to docs when relevant (@see).

Link to release checklist

When you are doing a doc / API freeze, also run through Pre-release / final pass checklist.