fix(session-query): harden SQLite search reconciliation

docs/core-data-structures/persistence.md

@@ -2,7 +2,7 @@
 
 The **durability seam** for the event log. [session.md](session.md) describes the in-memory `Session` — the append-only `SessionEvent` log that is the source of truth. This page describes how that log is made durable: the abstract `SessionPersistence` service, its backends, the flush checkpoint, crash recovery, and the metadata header that travels alongside the log. The event vocabulary the log carries is enumerated, member by member, in the generated [persistence log event catalog](../persistence-catalog.md).
 
-The seam is a textbook [capability seam](../rfc/implemented/architecture/2026-06-13-capability-seams.md): one abstract service ([dsh-session-persistence](../../packages/session-persistence/session-persistence), `ctx.sessionPersistence`) defining create/append/load/list over the existing `SessionEvent` — **no parallel persisted type** — and two interchangeable backends that pass the same `runPersistenceContract` suite. See the [session-persistence RFC](../rfc/implemented/architecture/2026-06-14-session-persistence.md).
+The seam is a textbook [capability seam](../rfc/implemented/architecture/2026-06-13-capability-seams.md): one abstract service ([dsh-session-persistence](../../packages/session-persistence/session-persistence), `ctx.sessionPersistence`) defining create/append/load plus lightweight list/snapshot observation over the existing `SessionEvent` — **no parallel persisted event type** — and two interchangeable backends that pass the same `runPersistenceContract` suite. See the [session-persistence RFC](../rfc/implemented/architecture/2026-06-14-session-persistence.md).
 
 ## The flush checkpoint
 
@@ -78,9 +78,24 @@ interface CreateSessionOptions {
 
 Replay/fork is therefore `ctx.sessions.create(id, { seed: seedEvents })`; resuming a *persisted* session into a live agent is `ctx.agents.resume({ resumeSessionId })`.
 
+## Lightweight source revisions
+
+Consumers of derived state compare a cheap opaque revision before loading a full event log. The persistence backend owns its representation and changes it transactionally with append or mutating load repair; callers compare it only for equality.
+
+```ts type-equiv
+export type SessionPersistenceRevision = Branded<'SessionPersistenceRevision'>
+```
+
+```ts type-equiv
+export interface SessionPersistenceSnapshot {
+  header: SessionHeader
+  revision: SessionPersistenceRevision
+}
+```
+
 ## The backends
 
-Both implement the same abstract `SessionPersistence` (create/append/load/list over `SessionEvent`) and pass `runPersistenceContract`, proving the seam is genuinely backend-agnostic:
+Both implement the same abstract `SessionPersistence` (create/append/load/list/listSnapshots over `SessionEvent`) and pass `runPersistenceContract`, proving the seam is genuinely backend-agnostic:
 
 - **[dsh-session-persistence-jsonl](../../packages/session-persistence/session-persistence-jsonl)** — an append-only JSONL log per session with crash-safe atomic writes, the interrupted-turn crash recovery above, and a read/replay path.
 - **[dsh-session-persistence-sqlite](../../packages/session-persistence/session-persistence-sqlite)** — `node:sqlite`, one row per `SessionEvent`. The row shape `(session_id, seq, type, time, data, source_event_seqs, surface_op)` maps 1:1 onto the event, including optional surface metadata, so there is no parallel persisted schema to keep in sync.

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

@@ -58,19 +58,23 @@ export interface SessionEventSearchDocument extends SessionEventRecord {
 }
 ```
 
-`ctx.sessionQuery.filterEvents(sessionId, filters)` returns these documents in ascending seq order. Messages, reasoning, tool calls/results, blocked prompts, todos, and failure/status detail contribute semantic text; structural events and stream chunks do not.
+`ctx.sessionQuery.filterSessions(filters)` applies `SessionResultFilter` to the complete logical corpus; `ctx.sessionQuery.filterEvents(sessionId, filters)` returns matching documents in ascending seq order. Messages, reasoning, tool calls/results, blocked prompts, todos, and failure/status detail contribute semantic text; structural events and stream chunks do not.
 
 ## Full-text search pages
 
 The independent `ctx.sessionSearch` seam has two scopes. `searchSessions()` groups the corpus by strongest matching event; `searchEvents()` searches one session. Requests bind an opaque cursor to the normalized query, metadata filters, and limit. The event text scan is intentionally absent from provider metadata filters.
 
+```ts type-equiv
+export type SessionSearchCursor = Branded<'SessionSearchCursor'>
+```
+
 ```ts type-equiv
 export interface SessionSearchRequest {
   query: string
   sessionFilters?: readonly SessionResultFilter[]
   eventFilters?: readonly SessionEventMetadataFilter[]
   limit?: number
-  cursor?: string
+  cursor?: SessionSearchCursor
 }
 ```
 
@@ -80,14 +84,14 @@ export interface SessionEventSearchRequest {
   query: string
   filters?: readonly SessionEventMetadataFilter[]
   limit?: number
-  cursor?: string
+  cursor?: SessionSearchCursor
 }
 ```
 
 ```ts type-equiv
 export interface SessionSearchPage<T> {
   items: readonly T[]
-  nextCursor?: string
+  nextCursor?: SessionSearchCursor
 }
 ```