phone: paint the durable proxy-gap row (#1381 follow-up)

[Juliusolsson05]

Follow-up of #1381 / PR #1442.

The desktop now paints a durable "Part of this response was not captured (HH:MM:SS–HH:MM:SS)" row where the Claude proxy transport lost live output. The phone receives the transport-gap channel (WebSocketSessionFeed.onSessionTransportGap, wire.ts FeedChannel), but its TranscriptStore neither subscribes nor reads SessionHistoryChunk.transportGaps from its initial history load. The phone feed therefore still shows the stitched answer with no row.

Fix shape:

• the TranscriptStore holds transportGaps the way the desktop runtime does (merged by record id);
• it passes them as RuntimeRenderInput.transportGaps;
• the shared ledger and Feed pipeline already render the row.

🤖 Generated with Claude Code

[Juliusolsson05]

Blocked (W2): the transportGaps channel and SessionHistoryChunk.transportGaps this needs exist only on W3's open #1442 (fix/claude-proxy-gap-marker), not on origin/main 6dd23a49. Suggest W3 takes it after #1442 merges, since it is that PR's follow-up and shares its types.