Trim comments across Rust and webapp source to direct one-liners (ticket 030)

Pass over src/*.rs, webapp/src/**, and the in-app "?" docs prose:
condensed multi-paragraph doc comments to single lines that state the
non-obvious why, deleted comments that only restated adjacent code, and
tightened the Docs.tsx help-panel wording. No logic, structure, or code
formatting changed — verified via cargo test (143 passed) and
tsc -b && vite build.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

webapp/src/lib/themes.ts

@@ -1,20 +1,4 @@
-/**
- * Downloadable/re-uploadable custom themes (ticket 033).
- *
- * A theme file is a small CSS file containing exactly one `:root { --c-*:
- * ...; }` block defining every variable in `THEME_CSS_VARS` (the full set
- * `index.css`'s `:root`/`html.<scheme>` blocks use to skin the app). Using
- * `:root` (rather than a scoped selector) keeps the file trivially portable:
- * the same content works whether it's applied at `:root` or scoped, and
- * round-tripping a downloaded file back through upload reproduces it
- * byte-for-byte-equivalent (same variable values).
- *
- * Applying a selected custom theme is left to `useSettingsPanel`, which
- * injects the entry's CSS as an unscoped stylesheet *only* while no built-in
- * `html.<scheme>` class is present — since both forms target `:root` with
- * equal specificity, the later stylesheet in the cascade wins, so no
- * rewriting of the file's own `:root` selector is needed.
- */
+// A theme file is a CSS file with one `:root { --c-*: ...; }` block defining every variable in `THEME_CSS_VARS`; `useSettingsPanel` applies the selected one as an unscoped stylesheet only while no built-in `html.<scheme>` class is present, so it wins the cascade without rewriting the selector.
 
 /** Canonical list of every `--c-*` variable every theme in `index.css` defines. */
 export const THEME_CSS_VARS = [
@@ -42,16 +26,7 @@ export const THEME_CSS_VARS = [
 
 export type ThemeVars = Record<(typeof THEME_CSS_VARS)[number], string>
 
-/**
- * Built-in themes' fully-resolved variable values, matching `index.css`'s
- * current cascade (a theme that doesn't override `--c-danger-*` there falls
- * back to `:root`'s dark values there, so those are inlined here too — a
- * downloaded built-in file is always complete, never relies on a `:root`
- * fallback the download mechanism doesn't have access to).
- *
- * Keep in sync with `webapp/src/index.css` by hand; there's no built step
- * that derives one from the other.
- */
+// Fully-resolved variable values for each built-in theme, including inherited fallbacks, so a downloaded file is always complete; keep in sync with `index.css` by hand, there's no build step linking the two.
 export const BUILTIN_THEMES: Record<string, ThemeVars> = {
   dark: {
     '--c-surface-0': '#0a0a0a',
@@ -253,7 +228,6 @@ export const BUILTIN_THEMES: Record<string, ThemeVars> = {
   },
 }
 
-/** Generates a downloadable theme CSS file's content from a full variable map. */
 export function generateThemeCss(vars: ThemeVars): string {
   const lines = THEME_CSS_VARS.map((name) => `  ${name}: ${vars[name]};`)
   return `:root {\n${lines.join('\n')}\n}\n`
@@ -264,14 +238,7 @@ export interface ParsedTheme {
   missing: string[]
 }
 
-/**
- * Parses a theme CSS file's content, pulling `--c-*: value;` declarations
- * out of its first `:root { ... }` block (or, failing that, out of the
- * whole file — tolerant of a hand-edited file that dropped the selector).
- * Returns every recognized variable found plus the list of canonical
- * variables (see `THEME_CSS_VARS`) that were missing, so callers can reject
- * an incomplete upload with a clear error.
- */
+// Parses `--c-*: value;` declarations from the first `:root { ... }` block (or the whole file, tolerant of a dropped selector); reports missing canonical variables so callers can reject an incomplete upload.
 export function parseThemeCss(content: string): ParsedTheme {
   const rootMatch = content.match(/:root\s*\{([^}]*)\}/)
   const body = rootMatch ? rootMatch[1] : content
@@ -286,7 +253,6 @@ export function parseThemeCss(content: string): ParsedTheme {
   return { vars, missing }
 }
 
-/** Triggers a browser download of `content` as `filename` (a `.css` file). */
 export function downloadThemeFile(filename: string, content: string) {
   const blob = new Blob([content], { type: 'text/css' })
   const url = URL.createObjectURL(blob)