fix: bind session authorization to observations

docs/core-data-structures/session-query.md

@@ -39,6 +39,18 @@ interface SessionSurfaceSnapshot {
 }
 ```
 
+`SessionTitleObservation` applies the same atomic-observation rule to title folding, so an authorization consumer can validate the source header that supplied the title.
+
+```ts type-equiv
+/** Latest folded title bound to the same session-header observation. */
+interface SessionTitleObservation {
+  /** Cloned header selected with the event log used for the title fold. */
+  session: SessionHeader
+  /** Latest title snapshot, absent when the observed log has no title. */
+  title?: SessionTitleSnapshot
+}
+```
+
 ```ts type-equiv
 /** Lightweight metadata for one event within a logical session. */
 interface SessionEventRecord {
@@ -146,6 +158,16 @@ interface SessionSearchPage<T> {
 }
 ```
 
+Unlike grouped cross-session hits, a within-session search must also expose its observed target header even when the page contains no hits.
+
+```ts type-equiv
+/** Event-search results bound to the indexed target-session observation. */
+interface SessionEventSearchPage extends SessionSearchPage<SessionEventSearchHit> {
+  /** Cloned target header from the same indexed generation as `items`. */
+  session: SessionHeader
+}
+```
+
 ```ts type-equiv
 /** One event full-text search hit with a bounded plain-text excerpt. */
 interface SessionEventSearchHit extends SessionEventRecord {
@@ -267,6 +289,14 @@ interface SessionEventTrace {
 }
 ```
 
+```ts type-equiv
+/** Event relationships bound to the same session-header observation. */
+interface SessionEventTraceObservation extends SessionEventTrace {
+  /** Cloned header selected with the event log used for the trace. */
+  session: SessionHeader
+}
+```
+
 ## Errors
 
 The closed code union distinguishes request validation, missing targets, malformed surface logs, optional-backend failure, and contradictory source metadata.