Gate iMessage same-sender DM split-send coalescing on imsg's structural
`balloon_bundle_id` URL-balloon marker (openclaw/imsg#137) instead of timing/
text-shape inference, with a session capability latch and a back-compat path:
- URL-balloon marker present -> merge (precise split-send).
- Build known to emit balloon metadata (session latch) -> keep non-marker
buckets separate (the precision win).
- Build that never emits balloon metadata (older imsg) -> preserve the legacy
unconditional merge, so split-send users do not regress to two turns.
Never merges more than shipped main already did. Verified live end-to-end: the
patched gateway, watching a real chat.db via an imsg #137 build, merged a real
iPhone-sent `Dump <url>` split-send into one turn. Client-side removal once imsg
coalesces upstream is tracked in #91243 (openclaw/imsg#141).
Closes#90795
Omar Shahine
9caff5f873