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

src/metric_primitive.rs

@@ -10,9 +10,7 @@ pub enum MetricPrimitive {
     String(String),
     Number(Number),
     Timestamp(Timestamp),
-    /// Milliseconds elapsed (ticket 023). Distinct from `Number` so a
-    /// duration reads unambiguously in JSON/label form, even though it's
-    /// stored the same way (a plain `i64`).
+    /// Milliseconds elapsed; distinct from `Number` so it reads unambiguously in JSON/label form.
     Duration(i64),
 }
 
@@ -49,10 +47,7 @@ impl Ord for MetricPrimitive {
     }
 }
 
-/// Textual form used for label-filter comparisons over the metrics API
-/// (`GET /api/metrics/:name?labels=foo=bar`): query-string values are plain
-/// strings, so a label filter is compared against this formatted form rather
-/// than trying to parse the filter value into a typed `MetricPrimitive`.
+/// Textual form used to compare label filters (query-string values) against a formatted `MetricPrimitive` rather than parsing them into one.
 impl fmt::Display for MetricPrimitive {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
@@ -74,10 +69,7 @@ pub enum Number {
 }
 
 impl Number {
-    /// Widens to `f64` for cross-kind numeric comparisons (e.g. a filter
-    /// query's `FilterValue::Number` against a declared metric's captured
-    /// `Number`). `pub(crate)` rather than private since ticket 007's filter
-    /// evaluator (in `engine.rs`) needs it and lives in a different module.
+    /// Widens to `f64` for cross-kind numeric comparisons; `pub(crate)` since the filter evaluator in `engine.rs` needs it.
     pub(crate) fn as_f64(&self) -> f64 {
         match self {
             Number::Int(v) => *v as f64,