v3: comments say what the code can't — the documentation pass wanted JSDoc on every export and every field of an exported interface, which filled the code with restatements ("The dump.", "Whether it is loading.", "The props of X.", "Renders the X.") and module docs that told a reader nothing ("The hot and new feeds, and the props every main feed of the index takes."); some were wrong as well as vague. Every comment in api/, shared/ and src/ is rewritten under one rule, now stated in the README's "Comments" section: every module and export still has a JSDoc, and it gives context (who uses it and where), usage (what a caller must know: a precondition, what it leaves to the caller, a side effect) or its place in the chain (where its input comes from, where its output goes); a field, parameter, private function or local gets one only when it adds to its parent's, and context about a whole type goes on the type; a type's doc is phrased from the value's side ("Returned to Y by X when Z", "Passed to Y by X"); full sentences, as short as they can be, no label-colon-list; // goes wherever the code isn't obvious and says why, and the section banners and narration go. Every claim was checked against the code, which turned up some forty comments that were wrong: DumpCard's claimed it was only used by the hot and new feeds, the WebSocket welcome claimed to be a socket's first message (presence comes first), UpdateUserRequest said null removes a description (it keeps it), deletedDumpIds leaves out that it also holds dumps made private, THEME_COLOR claimed to mirror index.html's, and the like. The routers' JSDoc now says where they are mounted and what becomes of a thrown APIException. doc-lint.ts lets a field without a doc through; a module or export without one still fails. No code changes; 204 backend and 628 frontend tests pass, and doc:lint, deno check, deno lint and tsc are clean.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/lib/reserved-slugs.ts

@@ -1,13 +1,16 @@
 /**
- * Which slugs a category may take. Category slugs live at the URL root (e.g.
- * /music), so they must never collide with the frontend's own routes.
+ * Checks which slugs a category may take. A category's feed lives at the URL
+ * root (`/music`), so its slug must not shadow another top-level route. The
+ * category service runs these checks when a category is created or renamed.
  *
  * @module
  */
 
 /**
- * Top-level path segments that already have meaning in the SPA router (see
- * src/App.tsx), plus a few reserved for infrastructure.
+ * The top-level path segments a category slug may not take. They are the SPA's
+ * own routes (`src/App.tsx`), `api` and `assets`, which the server answers
+ * before the SPA, and `manage`, which no route uses any more. Keep it in step
+ * with the route table.
  */
 export const RESERVED_SLUGS: readonly string[] = [
   "~",
@@ -25,12 +28,12 @@ export const RESERVED_SLUGS: readonly string[] = [
 ];
 
 /**
- * A well-formed category slug: lowercase alphanumerics,
- * hyphen-separated, no leading, trailing or double hyphen.
+ * Matches a well-formed category slug, made of lowercase letters and digits
+ * joined by single hyphens.
  */
 export const CATEGORY_SLUG_RE = /^[a-z0-9]+(?:-[a-z0-9]+)*$/;
 
-/** Checks whether `slug` is well-formed (see {@link CATEGORY_SLUG_RE}). */
+/** Checks whether `slug` matches {@link CATEGORY_SLUG_RE}. */
 export function isValidSlugFormat(slug: string): boolean {
   return CATEGORY_SLUG_RE.test(slug);
 }
@@ -40,7 +43,10 @@ export function isReservedSlug(slug: string): boolean {
   return RESERVED_SLUGS.includes(slug);
 }
 
-/** Checks whether `slug` is well-formed and not reserved. */
+/**
+ * Checks whether `slug` is well-formed and not reserved. The category service
+ * runs the two checks apart, to give each failure its own message.
+ */
 export function isSlugAvailable(slug: string): boolean {
   return isValidSlugFormat(slug) && !isReservedSlug(slug);
 }