feat(fix-a3): rename TransferredVideoChunk → TransferredVideoSegment

Pure rename pass — zero behavioural change at any call site. The
prior "chunk" naming is a vestige of D-09..D-11's chunk-level
buffer; under D-13 the unit of transfer is a self-contained ~10 s
WebM segment, so the type name now matches the data shape.

Renames propagated atomically:
- src/shared/types.ts
  * TransferredVideoChunk → TransferredVideoSegment
    (also: the `isFirst?: boolean` field is dropped — D-13 segments
    are all implicitly their own header, so the flag is meaningless
    and only existed for the retired ring-buffer's pin semantics)
  * VideoChunk → VideoSegment (drops `isFirst?` for the same reason)
  * PortMessage.chunks? → PortMessage.segments?
  * VideoBufferResponse.chunks → VideoBufferResponse.segments
- src/offscreen/recorder.ts
  * import type rename
  * encodeAndSendBuffer's per-element accumulator + filter type
  * the port.postMessage payload field
- src/background/index.ts
  * import type rename
  * getVideoBufferFromOffscreen reads `(msg as {segments?}).segments`
    (matching the new wire field name)
  * empty-buffer returns `{ segments: [] }`
  * mergeVideoSegments signature takes VideoSegment[]
  * createArchive consumes videoBufferResponse.segments
  * saveArchive log line says "segments"

Verification:
- npx tsc --noEmit clean.
- npx vitest run → 28 passed / 2 failed (the 2 fixture-empirical
  ffmpeg dry-runs; unchanged — they're gated on ./smoke.sh regen).
- npm run build succeeds, all 60 modules transformed.
- grep predicates clean in src/:
  * no addChunk / trimAged / firstChunkSaved / isFirst
  * no TransferredVideoChunk / VideoChunk (old names)
  * 21 occurrences of new names propagated correctly
- Pre-existing port-serialization.test.ts still GREEN: its `isFirst`
  references are inside inline-test-scoped objects (not imports
  from production types), and its tests assert JSON-roundtrip
  behaviour rather than the production type shape.

src/background/index.ts

@@ -2,8 +2,8 @@ import { Logger } from '../shared/logger';
 import { base64ToBlob } from '../shared/binary';
 import type {
   Message,
-  TransferredVideoChunk,
-  VideoChunk,
+  TransferredVideoSegment,
+  VideoSegment,
   SessionMetadata,
   VideoBufferResponse
 } from '../shared/types';
@@ -105,14 +105,14 @@ const BUFFER_FETCH_TIMEOUT_MS = 2_000;
 async function getVideoBufferFromOffscreen(): Promise<VideoBufferResponse> {
   if (videoPort === null) {
     logger.warn('No offscreen port available; returning empty buffer');
-    return { chunks: [] };
+    return { segments: [] };
   }
   const port = videoPort;
   return new Promise<VideoBufferResponse>((resolve) => {
     const timer = setTimeout(() => {
       port.onMessage.removeListener(handler);
       logger.warn(`Buffer fetch timed out after ${BUFFER_FETCH_TIMEOUT_MS} ms`);
-      resolve({ chunks: [] });
+      resolve({ segments: [] });
     }, BUFFER_FETCH_TIMEOUT_MS);
     const handler = (msg: unknown) => {
       if (
@@ -122,20 +122,19 @@ async function getVideoBufferFromOffscreen(): Promise<VideoBufferResponse> {
       ) {
         clearTimeout(timer);
         port.onMessage.removeListener(handler);
-        // D-12 wire format: payload arrives as TransferredVideoChunk[]
-        // — base64 string + MIME — because chrome.runtime.Port
-        // JSON-serializes across extension contexts. Decode each entry
-        // back into a VideoChunk. D-13 lifecycle: each entry is now a
-        // self-contained WebM segment (~10 s, EBML header + seed
-        // keyframe), not a partial chunk; concatenating them
-        // sequentially produces a multi-EBML-header file Chrome plays
-        // natively. See src/shared/binary.ts + RESEARCH.md Pattern 3.
+        // D-12 wire format + D-13 segment lifecycle: payload arrives
+        // as TransferredVideoSegment[] (base64 string + MIME). Decode
+        // each entry back into a VideoSegment — each is a
+        // self-contained ~10 s WebM (EBML header + seed keyframe).
+        // Concatenating them sequentially produces a multi-EBML-header
+        // file Chrome plays natively. See src/shared/binary.ts +
+        // RESEARCH.md Pattern 3.
         const wireSegments =
-          (msg as { chunks?: TransferredVideoChunk[] }).chunks ?? [];
-        const chunks: VideoChunk[] = [];
+          (msg as { segments?: TransferredVideoSegment[] }).segments ?? [];
+        const segments: VideoSegment[] = [];
         for (const wire of wireSegments) {
           try {
-            chunks.push({
+            segments.push({
               data: base64ToBlob(wire.data, wire.type || VIDEO_MIME_FALLBACK),
               timestamp: wire.timestamp,
             });
@@ -147,7 +146,7 @@ async function getVideoBufferFromOffscreen(): Promise<VideoBufferResponse> {
             );
           }
         }
-        resolve({ chunks });
+        resolve({ segments });
       }
     };
     port.onMessage.addListener(handler);
@@ -238,7 +237,7 @@ async function captureScreenshot(): Promise<Blob> {
 
 // Склейка сегментов в один WebM-файл.
 //
-// Под D-13 каждый VideoChunk — это самодостаточный ~10-секундный WebM
+// Под D-13 каждый VideoSegment — это самодостаточный ~10-секундный WebM
 // (собственный EBML-заголовок + seed keyframe). Сортируем по timestamp
 // и склеиваем подряд: получаем multi-EBML-header файл, который Chrome
 // проигрывает последовательно (см. SPEC §10 #7 — требуется проигрывание
@@ -246,7 +245,7 @@ async function captureScreenshot(): Promise<Blob> {
 //
 // Никакой логики «pin первого чанка» или header-retention больше нет
 // — это снято вместе с D-09..D-11 и активацией D-13 в recorder.ts.
-function mergeVideoSegments(segments: VideoChunk[]): Blob {
+function mergeVideoSegments(segments: VideoSegment[]): Blob {
   logger.log(`Merging ${segments.length} segments`);
 
   // Сортируем по времени, чтобы сохранить правильный порядок (старшие
@@ -286,9 +285,9 @@ async function createArchive(
 
   const zip = new JSZip();
 
-  // Добавляем видео (D-13: чанки в ответе — это уже сегменты)
-  if (videoBufferResponse.chunks.length > 0) {
-    const videoBlob = mergeVideoSegments(videoBufferResponse.chunks);
+  // Добавляем видео (D-13: каждая запись — самодостаточный WebM-сегмент)
+  if (videoBufferResponse.segments.length > 0) {
+    const videoBlob = mergeVideoSegments(videoBufferResponse.segments);
     zip.file('video/last_30sec.webm', videoBlob);
     logger.log(`✓ Added video: ${videoBlob.size} bytes`);
   } else {
@@ -386,7 +385,7 @@ async function saveArchive() {
 
     // Получаем видео буфер из offscreen через long-lived port (D-17)
     const videoBufferResp = await getVideoBufferFromOffscreen();
-    logger.log(`Video buffer: ${videoBufferResp.chunks.length} chunks`);
+    logger.log(`Video buffer: ${videoBufferResp.segments.length} segments`);
 
     // Получаем rrweb события от content script
     logger.log(`Requesting rrweb events from content script on tab ${tab.id} (${tab.url})...`);