docs: cut the comments that were not earning their place

I wrote 731 comment lines on this branch against 4,530 lines of code — 14%,
where the rest of the repo runs at 1.8%. CLAUDE.md asks for code that reads
like its surroundings, and this did not.

Removed by genre rather than by taste:

- restating the code, e.g. "JS getUTCDay() numbering: Sunday = 0" above the
  map that literally shows it, and a docblock on startOfWeek explaining that
  it returns the start of the week;
- narrating history — "this used to rebuild the whole map", "left the bar
  recording forever" — which the commit message and git blame already carry;
- saying the same thing in several places: the "cannot record is not a
  denied microphone" reason appeared three times in one file, and the
  "aborting stops a per-minute metered call" reason across three files. Each
  now lives once, where the behaviour it explains lives;
- defending decisions nobody would question, like why toLatinDigits is its
  own module;
- over-explaining defensive branches, three separate comments to distinguish
  null from missing-kind from unrecognised-kind.

What stays is what the code cannot say: the patient-right convention in
toFdi, whose failure mode is a valid code for the wrong tooth; the
"this"-vs-"next" week anchoring; StrictMode re-arming mountedRef; Safari
accepting no mimeType hint; and the invariants whose violation already cost
a bug — the body parser's middleware ordering and the dispatch panel's
auto-fill rules.

Comments only. The diff contains no non-comment line.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

backend/src/modules/voice/extraction.wire.ts

@@ -10,13 +10,10 @@ import type {
 import { WEEKDAYS } from './voice.types';
 
 /**
- * The shape the model actually emits, and its JSON schema.
- *
  * Deliberately flat: strict `json_schema` mode has poor support for discriminated unions,
- * so every variant field is present and nullable on the wire. `toVoiceIntent` narrows the
- * flat shape into the internal union the resolvers consume, and is total — anything it
- * cannot classify becomes a shape the resolvers will report as unresolved rather than
- * something that throws here.
+ * so every variant field is present and nullable. `toVoiceIntent` narrows it into the
+ * internal union and is total — anything it cannot classify becomes a shape the resolvers
+ * report as unresolved rather than something that throws here.
  */
 
 export type WireToothIntent = {
@@ -183,9 +180,8 @@ const FDI_SHAPE = /^[1-8][1-8]$/;
 
 function toToothIntent(wire: WireToothIntent | undefined | null): ToothIntent {
   const spoken = typeof wire?.spoken === 'string' ? wire.spoken : '';
-  // Persian digits and digit-by-digit dictation ("۲۶", "2 6") are FDI codes that do not
-  // match literally; without normalising first they fall through to the positional branch
-  // with no quadrant and are reported as unresolved.
+  // "۲۶" and "2 6" are FDI codes that do not match literally; unnormalised they fall
+  // through to the positional branch with no quadrant and read as unresolved.
   const fdi = normalizeFdiCode(wire?.fdi);
   // Only take the explicit branch for something actually FDI-shaped. A model that emits
   // fdi:"6" alongside correct arch/side/position would otherwise lose the tooth entirely.