fix(stats): harden duplicate-line cleanup and tracking

- Reject malformed requests and sub-day cleanup windows
- Reset deduplication across media and subtitle-track changes
- Handle karaoke bursts ending with a long hold frame

launcher/config/cli-parser-builder.ts

@@ -56,12 +56,12 @@ export interface CliInvocations {
   texthookerOpenBrowser: boolean;
 }
 
-/** `--lookback-days` narrows the duplicate-line cleanup; anything unusable means no limit. */
+/** `--lookback-days` narrows the duplicate-line cleanup; fractions are floored. */
 function parseStatsLookbackDays(value: unknown): number | null {
   if (typeof value !== 'string' && typeof value !== 'number') return null;
   const days = Number(value);
-  if (!Number.isFinite(days) || days <= 0) {
-    throw new Error('Stats --lookback-days must be a positive number of days.');
+  if (!Number.isFinite(days) || days < 1) {
+    throw new Error('Stats --lookback-days must be at least one day.');
   }
   return Math.floor(days);
 }

launcher/parse-args.test.ts

@@ -244,6 +244,13 @@ test('parseArgs maps duplicate-line stats cleanup flags', () => {
   assert.equal(parsed.statsCleanupDuplicateLines, true);
   assert.equal(parsed.statsCleanupDryRun, true);
   assert.equal(parsed.statsCleanupLookbackDays, 30);
+
+  const fractional = parseArgs(
+    ['stats', 'cleanup', '--duplicate-lines', '--lookback-days', '1.5'],
+    'subminer',
+    {},
+  );
+  assert.equal(fractional.statsCleanupLookbackDays, 1);
 });
 
 test('parseArgs rejects duplicate-line flags without the duplicate-lines mode', () => {
@@ -265,7 +272,7 @@ test('parseArgs rejects combining lifetime and duplicate-line cleanup modes', ()
 });
 
 test('parseArgs rejects unusable lookback windows', () => {
-  for (const value of ['0', '-5', 'soon']) {
+  for (const value of ['0', '0.5', '-5', 'soon']) {
     const error = withProcessExitIntercept(() => {
       parseArgs(
         ['stats', 'cleanup', '--duplicate-lines', '--lookback-days', value],
@@ -275,7 +282,7 @@ test('parseArgs rejects unusable lookback windows', () => {
     });
 
     assert.equal(error.code, 1);
-    assert.match(error.stderr, /--lookback-days must be a positive number of days/);
+    assert.match(error.stderr, /--lookback-days must be at least one day/);
   }
 });