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/components/Metrics.tsx

@@ -15,9 +15,7 @@ import { HelpIcon } from './HelpIcon'
 
 const EMPTY_MATCHER: MetricParamMatcher = { param_name: '', capture_group: '', kind: 'string' }
 
-/// One row in the "labels -> occurrence count" table for the selected
-/// metric's bucket values over the active range. `values` keeps the raw
-/// points (used for the sparkline-ish rendering) alongside the count.
+// One row in the labels -> occurrence count table; `values` keeps the raw points for the sparkline rendering.
 interface LabelGroup {
   key: string
   labels: Record<string, string>
@@ -52,9 +50,7 @@ function groupByLabels(values: BucketValue[]): LabelGroup[] {
   return Array.from(groups.values()).sort((a, b) => b.count - a.count)
 }
 
-/// A crude text sparkline: buckets a group's values into a fixed number of
-/// slots across the visible range and renders relative bar heights using
-/// block characters. Not a real chart — that's ticket 014's job.
+// A crude text sparkline using block characters — not a real chart, that's ticket 014's job.
 const SPARK_CHARS = ' ▁▂▃▄▅▆▇█'
 function sparkline(values: BucketValue[], range: TimeRange | null): string {
   if (values.length === 0) return ''
@@ -98,11 +94,7 @@ export function Metrics({ range }: { range: TimeRange | null }) {
     loadMetrics()
   }, [])
 
-  // Refetch-on-change rather than continuous polling: bucket values only
-  // need to move when the selected metric or the active time range
-  // changes, and a declaration's backfill (ticket 003) is already reflected
-  // by the time `declareMetric`'s promise resolves, so there's no need for
-  // an interval here the way `App.tsx`'s log/timeline polling has.
+  // Refetch-on-change rather than continuous polling: bucket values only move when the selected metric or range changes, so no interval is needed here like `App.tsx`'s log/timeline polling.
   useEffect(() => {
     if (!selected) {
       setBucketValues([])