fix(voice): make viewport escalation diagnostics truthful and paired

Review follow-up for #835. What is captured, sent and kept is unchanged.

- Log nothing for tool results other than get_entity_context, so other
  tools stop spending the shared debug-log budget.
- Give every decision and outcome the same contextId and image kind, so
  overlapping requests pair up.
- Log why a crop decision did not send (stale, off ground, off screen,
  expired, pose changed, already requested) instead of leaving a lone
  "pointer-ground-crop" that reads as sent.
- Split capture-invalidated into session-reset, superseded, channel-lost
  and frame-stale.
- Close the pair with "error" when a step throws, then rethrow.
- Document the events in CURRENT-STATE and reword the changelog fragment.

changelog.d/835-viewport-escalation-reasons.md

@@ -1,5 +1,7 @@
-- Voice viewport escalation now emits compact reason-code diagnostics without
-  recording tool payloads. The policy still prefers structured entity identity,
-  preserves the live point-and-ask crop added in #837, and does not add image
-  requests, change image retention or automatically widen visual scope.
-  This follows asturksever's #835 review; credit the #837 pointer-crop authors.
+- The voice debug log now says why OpenAI Realtime did or did not get a
+  viewport screenshot or pointer crop. Each entity-context answer logs a
+  reason-coded decision and, when an image was due, one outcome under the same
+  id, so a crop that was dropped because the pointer went stale or the camera
+  moved is no longer counted as sent. What is captured, sent and kept is
+  unchanged, and no image data or user text is logged (kvnloo, manjunath22466,
+  #835).