Change details: labelled APDU/time in the header, no zero counts (v2.7.4)

- the header's trailing meta is labelled instead of bare numbers:
  "ADF/EF_IMSI (6F07) — READ BINARY · APDU #490 · 0251.199 sec" (the record
  part already read "Record 2 / 5")
- the summary counts only what happened: "{c} bytes changed · {n} bytes newly
  observed" drops whichever part is zero ("4 bytes changed" alone when nothing
  was first observed) and an empty diff reads "No changes" instead of
  "0 bytes changed, 0 bytes newly observed"
- i18n: the combined key splits into '{c} bytes changed' / '{n} bytes newly
  observed' plus 'No changes', 'APDU' and 'sec' ('{c}','{n}' placeholders keep
  the existing replace-based substitution; the Russian keeps the established
  wording: «Изменено байт: {c}», «Впервые наблюдается байт: {n}», «с»)
- tests: the header and summary assertions follow the labels, a short-file
  case pins the omitted zero, and an empty-diff case pins 'No changes';
  527 Python + 76 Node tests
- PWA_VERSION/pyproject/version.py 2.7.4, SW cache simtrace-analyser-v84

frontend/tests/comprion.test.js

@@ -379,7 +379,7 @@ test('Files view: strings carry Russian translations', () => {
 	for (const s of ['Files', 'Read', 'Update', 'Changed on card!', 'Change details',
 		'Show diff', 'Close', 'Offset', 'Record', 'Before', 'After', 'Show the change',
 		'changed', 'newly observed', 'never observed',
-		'{c} bytes changed, {n} bytes newly observed',
+		'{c} bytes changed', '{n} bytes newly observed', 'No changes', 'sec',
 		'Showing the first {n} bytes of the image',
 		'The image is frozen (size cap reached) — later changes are not tracked.',
 		'No file operations recorded', 'Failed to load files', 'Loading…']) {
@@ -508,9 +508,10 @@ test('Change details modal: header, summary, legend and both views', () => {
 	});
 	const sub = el('file-diff-sub').textContent;
 	assert.match(sub, /MF\/EF_ICCID \(2FE2\) — READ BINARY/);
-	assert.match(sub, /#12/);
+	assert.match(sub, /APDU #12/);
+	assert.match(sub, /0003\.250 sec/);
 	const body = el('file-diff-body').innerHTML;
-	assert.match(body, /2 bytes changed, 4 bytes newly observed/);
+	assert.match(body, /2 bytes changed · 4 bytes newly observed/);
 	assert.match(body, /hex-cell hex-changed/);     // legend + the changed byte
 	assert.match(body, /hex-cell hex-new/);
 	assert.match(body, /hex-cell hex-unknown/);
@@ -542,6 +543,8 @@ test('Change details: a short file shows no filler, no offset, no stray legend',
 	const body = el('file-diff-body').innerHTML;
 	assert.doesNotMatch(body, /hex-unknown/);      // no '--' cells at all
 	assert.doesNotMatch(body, /hex-addr/);         // a single row: no offset column
+	// The summary mentions only what happened.
+	assert.match(body, /^<div class="hex-summary">1 bytes changed<\/div>/);
 	assert.match(body, /hex-cell hex-changed/);
 	// The legend lists only what the views show: 'changed' (the summary line
 	// above still counts the zero "newly observed" bytes).
@@ -551,6 +554,17 @@ test('Change details: a short file shows no filler, no offset, no stray legend',
 	assert.doesNotMatch(legend, /newly observed|never observed/);
 });
 
+test('Change details: an empty diff says so instead of counting zeros', () => {
+	renderFileDiff({
+		name: 'EF_ICCID', path: 'MF/EF_ICCID (2FE2)', op: 'READ BINARY',
+		record: null, size: 2, index: 1, elapsed: 0.5, ranges: [],
+		observed_ranges: [], before: [{offset: 0, hex: 'aaaa'}],
+		after: [{offset: 0, hex: 'aaaa'}], image_truncated: false,
+	});
+	assert.match(el('file-diff-body').innerHTML,
+		/^<div class="hex-summary">No changes<\/div>/);
+});
+
 test('Change details: a short record keeps its never-observed tail', () => {
 	// A 9-byte record with 4 bytes observed: the row ends at 9 (no filler
 	// past it) and '--' marks the bytes that were never observed.