Restore calibration parity: revert unit-stripping from normaliseCal, fix CSV quoting at export

Finding 1: revert the comma/quote strip added in 3cb998c from
normaliseCal() in calibration.js. The strip broke byte-identical parity
with Go CalConfig.Normalise and C++ StreamHub::SetCalibrationEntry, both
of which only trim whitespace and cap at 16 UTF-8 bytes. Delete the
companion test that asserted the now-removed behaviour (suite returns to
18 tests).

Finding 2: fix the actual CSV-safety problem at the point of use in
exportAllCSV() in app.js. Header cells (time column and signal columns)
are now RFC 4180-quoted: wrapped in double quotes with any embedded
double quote doubled. This safely handles units or signal names that
contain commas or quotes without touching normaliseCal.

Finding 3: update two stale comments in app.js that called the trigger
threshold or rawFromNorm result 'raw' — Task 9 moved trig.threshold into
calibrated units throughout, so the comments now say 'calibrated'.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Client/udpstreamer/static/app.js

@@ -1343,7 +1343,7 @@ function drawTriggerMarker(u, p) {
   ctx.fillText('T', px + 3, bbox.top + 2);
   // Horizontal threshold line — only on plots that contain the trigger signal
   if (p && trig.signal && p.traces.includes(trig.signal)) {
-    // Normalize the raw threshold to this plot's vscale for the trigger signal.
+    // Normalise the calibrated threshold to this plot's vscale for the trigger signal.
     const tvs = p ? sigVScale[p.id + ':' + trig.signal] : null;
     let threshNorm = trig.threshold;
     if (tvs) {
@@ -2405,7 +2405,7 @@ function updatePlotCursorReadouts() {
 }
 
 /* ─── Hover readout ──────────────────────────────────────────────────────── */
-// Un-normalize a plotted value of trace `key` in plot `p` back to raw units.
+// Un-normalize a plotted value of trace `key` in plot `p` back to calibrated units.
 function rawFromNorm(p, key, vNorm) {
   const vs = sigVScale[p.id + ':' + key];
   if (!vs) return vNorm;
@@ -3052,9 +3052,11 @@ async function exportAllCSV() {
   const displayKeys = keys.map(k => {
     const name = k.includes(':') ? k.split(':').slice(1).join(':') : k;
     const u = unitForKey(k);
-    return u ? name + ' [' + u + ']' : name;
+    const h = u ? name + ' [' + u + ']' : name;
+    return '"' + h.replace(/"/g, '""') + '"';
   });
-  const hdr = [(inTrigMode ? 'time_rel_s' : 'time_s'), ...displayKeys].join(',');
+  const timeCol = '"' + (inTrigMode ? 'time_rel_s' : 'time_s') + '"';
+  const hdr = [timeCol, ...displayKeys].join(',');
   const rows = sortedT.map(t =>
     [t.toFixed(9), ...lookups.map((lk, i) =>
       lk.has(t) ? Calib.applyCal(lk.get(t), cals[i]) : '')].join(',')