Release exp-v0.52.264: fast regenerate via bounded sidecar-anchored tail read (#7204, @webtecnica)

Adds the CHANGELOG entry for #7204 (closes #6826). Release-metadata only;
the code change ships via the merge of #7204 (contributor webtecnica).

CHANGELOG.md

@@ -5,6 +5,8 @@
 
 ### Fixed
 
+- **Regenerating a response no longer refetches the entire conversation, so regenerate on a long chat is fast instead of stalling (and silently cancelling).** Clicking "regenerate" used to pull the whole transcript back from the server before it could rebuild the request, which on a large session caused a long UI freeze and could time out and silently drop the regeneration. The regeneration authority now reads only a bounded, sidecar-anchored tail of recent turns instead of the full transcript — and it is exact by construction: it takes the tail's prefix proof, keys, and rows from a single WAL-consistent database snapshot (a `data_version` check forces a full read if the database is written mid-snapshot), reuses the canonical projection and durable ordering so the bounded rows match the full reader byte-for-byte, and falls back to a full read whenever the skipped prefix isn't provably identical or the tail contains a duplicated turn key. If any of those invariants can't be met it reads the whole transcript exactly as before, so a concurrent edit or an unusual session can never produce a stale or reordered regeneration. Thanks @webtecnica. (#7204, closes #6826)
+
 - **Loading the session sidebar is faster on installs with many delegated-subagent sessions — the subagent classification no longer runs a separate database probe per row.** Building `/api/sessions` used to open a `state.db` connection for every session that might be a delegated child, an N+1 pattern that grew with session count. The classification now reads the authoritative `state.db` source for all candidate rows through the existing batched overlay (one read-only connection, chunked 500-ID `IN` queries), and a rich-read failure recovers the remaining IDs in a single bounded source-only pass rather than falling back to per-row queries. Behavior is unchanged — a delegated child whose index row still says `webui`/`fork` while its `state.db` source is `subagent` is classified read-only exactly as before. Thanks @starship-s. (#7231)
 
 - **Reopening a conversation that contains pasted or generated images no longer shows the same turn twice.** A native-image user turn is stored two ways — the rich WebUI sidecar row (with the actual image) and the Hermes Agent state row (the same turn as model-facing text, with each image replaced by `[screenshot]`) — and transcript reconciliation treated them as two different messages, so reopening the chat rendered a duplicate `[screenshot]` bubble under the real one. Reconciliation now recognizes the scalar state row as a mirror of the rich image row (matching on the exact `[screenshot]` projection, full-precision timestamp, role/tool shape, and provenance) and keeps only the rich row, so the image and its metadata survive and the duplicate is gone. It fails closed: a literal `[screenshot]` typed by the user, an ambiguous or conflicting identity match, a timestamp mismatch, or malformed content all preserve both rows rather than risk collapsing two genuinely different turns. Thanks @starship-s. (#7230)