correlator+summarizer: per-scene call-doc storage, fixes #96 and #114's real fix

Every scene of a multi-scene call correlates independently in upload.py's
scene loop, but every scene's corr_debug was written flat onto the same
shared call doc — scene 2's write silently clobbered scene 1's
corr_path/corr_consensus/etc (#96), and summarizer.py read the whole call's
raw transcript per linked call, mixing text from scenes the incident had
nothing to do with, while ignoring transcript_corrected entirely (#114).

Fix: thread a scene_index from both `for scene in scenes:` loops in
upload.py down through _correlate_with_consensus ->
incident_correlator.preview_correlation/correlate_call -> _build_context ->
ctx["scene_index"]. incident_correlator._apply_and_log now writes, in the
same Firestore call:
  - the existing flat corr_* fields, unchanged (last-scene-wins, the safe
    backward-compatible default for any reader that doesn't know about
    `scenes` yet)
  - a new nested `scenes.<scene_index>` entry with {transcript, incident_id,
    corr_debug}, via doc_set(..., merge=True). Firestore's
    DocumentReference.set(data, merge=True) recursively merges nested map
    fields by key (documented SDK behaviour, not assumed) — a write to
    scenes.1 merges alongside an existing scenes.0 instead of replacing the
    whole `scenes` map.
scene_index defaults to 0 for every caller with no scene concept (the
recorrelation sweep, the no-scenes-extracted orphan-check path), so a plain
single-scene call still gets a one-entry `scenes` map equivalent to reading
its flat fields today.

admin.py's _call_summary exposes the new `scenes` list per call (each entry
carrying the same corr_* field names as the flat fields, so the two shapes
are interchangeable to the tally); the summary tally now iterates each
call's scenes-if-present, else its own flat fields, so a 2-scene call with
two different corr_path values counts as two data points instead of one
blend. New `scene_decision_count` sits next to `linked_call_count` to make
that distinction visible.

summarizer.py's _scene_text_for_incident reads a linked call's `scenes` map
to find the scene(s) whose corr_debug recorded a link into the specific
incident being summarized, joining more than one if several scenes landed
in the same incident. Falls back to transcript_corrected-or-transcript for a
call doc with no `scenes` field (predates this change) — the one-liner half
of #114, worth doing regardless since it stops raw-transcript summaries even
for old-schema docs.

Does not touch #80/#95/#102's existing ctx-threading fixes
(embedding/severity/coords/LLM-prompt-transcript) — correct as-is, out of
scope here.

Tests: 14 new (test_per_scene_call_doc.py, test_summarizer_scene_transcript.py,
additions to test_admin_debug_correlation.py) covering the merge shape,
last-scene-wins flat-field backward compat, the admin tally's per-scene vs
per-call counting (including old-schema fallback), and the summarizer's
scene-specific text selection (including old-schema fallback). Full sandboxed
suite: 364 -> 378 passed, all green.

Fixes server-26#96, server-26#114

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Tbknwttzou4s46PAykmtix

drb-c2-core/app/routers/upload.py

@@ -240,6 +240,7 @@ async def _correlate_with_consensus(
     embedding: Optional[list] = None,
     severity: Optional[str] = None,
     transcript: Optional[str] = None,
+    scene_index: int = 0,
 ) -> Optional[str]:
     """
     Consensus correlator: runs the rules engine and the cheap LLM in sequence.
@@ -248,6 +249,11 @@ async def _correlate_with_consensus(
 
     Falls back to rules-only when GEMINI_API_KEY is absent, the call is
     content-free (thin), or any LLM call fails.
+
+    ``scene_index`` (server-26#96) — which scene of the call this is, from the
+    caller's ``enumerate(scenes)`` loop. Threaded through so the call doc's
+    per-scene ``scenes`` map records this scene's own corr_debug/transcript
+    instead of colliding with every other scene's write on the flat fields.
     """
     from app.internal import incident_correlator, llm_correlator
 
@@ -258,6 +264,7 @@ async def _correlate_with_consensus(
         location_coords=location_coords, units=units, vehicles=vehicles,
         cleared_units=cleared_units, reassignment=reassignment,
         embedding=embedding, severity=severity, transcript=transcript,
+        scene_index=scene_index,
     )
     ctx             = preview["ctx"]
     rules_decision  = preview["decision"]
@@ -365,7 +372,10 @@ async def _run_extraction_pipeline(
         )
 
         # Step 3: Correlate each scene to an incident independently.
-        for scene in scenes:
+        # server-26#96: scene_index is threaded through so each scene's
+        # corr_debug/transcript lands in its own entry of the call doc's
+        # `scenes` map instead of clobbering every other scene's write.
+        for scene_index, scene in enumerate(scenes):
             all_tags.extend(scene["tags"])
             # When dispatch is pulling a unit to a NEW call (reassignment), suppress unit
             # overlap so the new scene doesn't chain into the unit's previous incident.
@@ -388,6 +398,7 @@ async def _run_extraction_pipeline(
                 embedding=scene.get("embedding"),
                 severity=scene.get("severity"),
                 transcript=scene.get("transcript"),
+                scene_index=scene_index,
             )
             if incident_id and incident_id not in incident_ids:
                 incident_ids.append(incident_id)
@@ -485,7 +496,10 @@ async def _run_intelligence_pipeline(
     incident_ids: list[str] = []
     all_tags: list[str] = []
     if _flag("correlation_enabled"):
-        for scene in scenes:
+        # server-26#96: scene_index is threaded through so each scene's
+        # corr_debug/transcript lands in its own entry of the call doc's
+        # `scenes` map instead of clobbering every other scene's write.
+        for scene_index, scene in enumerate(scenes):
             all_tags.extend(scene["tags"])
             is_reassignment = bool(scene.get("reassignment"))
             corr_units = [] if is_reassignment else scene.get("units")
@@ -506,6 +520,7 @@ async def _run_intelligence_pipeline(
                 embedding=scene.get("embedding"),
                 severity=scene.get("severity"),
                 transcript=scene.get("transcript"),
+                scene_index=scene_index,
             )
             if incident_id and incident_id not in incident_ids:
                 incident_ids.append(incident_id)