fix(chat): keep a long turn's Edited N files card whole across the page cut (#86)

The reported turn (/vp-auto, ~120 messages) showed "Edited 1 file": the
chat loads the newest 50 messages, and the turn's other Write
(rbac_routes_test.go, +176) was in the part before the page.

- turnCarry (agent-edits.js): every message the route's sliding window
  drops goes through it; it keeps the file changes since the last prompt it
  dropped (a dropped call whose result is on the page, and dropped
  subagents, included).
- A Claude page that starts mid-turn answers them as `turn_edits`; the
  chat keeps the one from the page that holds its oldest message and adds
  it to that turn's card.

Files a turn changed through Bash (python/sed writing a file) are still not
listed: nothing in the transcript says which files a command wrote.

docs/API.md

@@ -2081,7 +2081,7 @@ GET /api/sessions/:id/transcript?agent_id=&run_id=&limit=&after=&before=&offset=
 
 `transcripts` lists the session's conversation files — the main one first, then each subagent's and compaction's — as `{ transcripts: [{ id, name, type: "main"|"subagent"|"compaction", subagent_type?, db_agent_id, … }] }`; `db_agent_id` links an entry to its `agents` row (`null` when none matches). A Codex, Antigravity, Cursor, omp or OpenCode session lists its own tool's journal instead.
 
-`transcript` reads one of them as structured messages: no `agent_id` = the main conversation, `agent_id` (+ `run_id` for a Workflow-tool agent) = a subagent's — each one plain name, never a path. `limit` defaults to 50 (max 200); `after=<line>` returns only messages past that JSONL line (the chat's tail), `before=<line>` the page before it (history), `offset` is the legacy pager. Answers `{ messages, total, has_more, last_line, first_line }` (empty when the file is gone). A Claude Agent/Task `tool_result` whose subagent (or one it started, up to 3 levels) wrote or edited files carries them as `edits: [{ path, added, removed, counted }]`, read from the subagent's own transcript (`server/lib/agent-edits.js`, cached by size + mtime) — the chat's "Edited N files" card counts them with the turn's own edits. The live file under the Claude projects folder is preferred, else the snapshot taken at import. `404 NOT_FOUND` for an unknown session.
+`transcript` reads one of them as structured messages: no `agent_id` = the main conversation, `agent_id` (+ `run_id` for a Workflow-tool agent) = a subagent's — each one plain name, never a path. `limit` defaults to 50 (max 200); `after=<line>` returns only messages past that JSONL line (the chat's tail), `before=<line>` the page before it (history), `offset` is the legacy pager. Answers `{ messages, total, has_more, last_line, first_line }` (empty when the file is gone). A Claude Agent/Task `tool_result` whose subagent (or one it started, up to 3 levels) wrote or edited files carries them as `edits: [{ path, added, removed, counted }]`, read from the subagent's own transcript (`server/lib/agent-edits.js`, cached by size + mtime) — the chat's "Edited N files" card counts them with the turn's own edits. A Claude page that starts in the middle of a turn also carries `turn_edits: [{ path, added, removed, counted }]` — the files that turn changed before the page's first message, gathered from the messages the page dropped — so the card stays whole when the turn is longer than `limit`. The live file under the Claude projects folder is preferred, else the snapshot taken at import. `404 NOT_FOUND` for an unknown session.
 
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