feat(session-query): add SQLite full-text search

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

@@ -1,6 +1,6 @@
 # Session Query
 
-Exact reads over the live-preferred logical session corpus. The [package contract](../../packages/session-query/session-query) owns source precedence, dynamic optional persistence, cloning, surface classification, bounded windows, and typed failures. Full-text search is a separate proposed SQLite phase.
+Query vocabulary over the live-preferred logical session corpus. The [interface package](../../packages/session-query/session-query) owns exact reads, source precedence, semantic extraction and provider-independent filters, while the [SQLite package](../../packages/session-query/session-query-sqlite) owns the concrete full-text index lifecycle.
 
 Source: [`packages/session-query/session-query/src/types.ts`](../../packages/session-query/session-query/src/types.ts)
 
@@ -30,6 +30,79 @@ export interface SessionEventRecord {
 }
 ```
 
+## Provider-independent filters and documents
+
+Session and event filter arrays are ANDed; values inside one list clause are ORed. Ranges are inclusive. The event `text` clause is a literal Unicode case-insensitive, whitespace-flexible regular-expression scan over extracted semantic text, independent of full-text providers.
+
+```ts type-equiv
+export type SessionResultFilter =
+  | { kind: 'id'; values: readonly SessionId[] }
+  | { kind: 'cwd'; values: readonly (string | null)[] }
+  | ({ kind: 'created-at' } & SessionResultRange)
+  | { kind: 'parent'; values: readonly (SessionId | null)[] }
+  | { kind: 'availability'; values: readonly SessionAvailability[] }
+```
+
+```ts type-equiv
+export type SessionEventResultFilter =
+  | ({ kind: 'seq' } & SessionResultRange)
+  | ({ kind: 'time' } & SessionResultRange)
+  | { kind: 'type'; values: readonly SessionEventType[] }
+  | { kind: 'surface'; values: readonly SessionEventSurface[] }
+  | { kind: 'text'; text: string }
+```
+
+```ts type-equiv
+export interface SessionEventSearchDocument extends SessionEventRecord {
+  text: string
+}
+```
+
+`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.
+
+## 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 interface SessionSearchRequest {
+  query: string
+  sessionFilters?: readonly SessionResultFilter[]
+  eventFilters?: readonly SessionEventMetadataFilter[]
+  limit?: number
+  cursor?: string
+}
+```
+
+```ts type-equiv
+export interface SessionEventSearchRequest {
+  sessionId: SessionId
+  query: string
+  filters?: readonly SessionEventMetadataFilter[]
+  limit?: number
+  cursor?: string
+}
+```
+
+```ts type-equiv
+export interface SessionSearchPage<T> {
+  items: readonly T[]
+  nextCursor?: string
+}
+```
+
+```ts type-equiv
+export interface SessionEventSearchHit extends SessionEventRecord {
+  snippet: string
+}
+```
+
+```ts type-equiv
+export interface SessionSearchHit extends SessionRecord {
+  bestMatch: SessionEventSearchHit
+}
+```
+
 ## Bounded event reads
 
 The request addresses one raw seq and optional neighboring counts. The result carries a `SessionHeader` rather than availability flags so a known live target can remain independent of persistence health.
@@ -59,11 +132,18 @@ The closed code union distinguishes request validation, missing targets, malform
 
 ```ts type-equiv
 export type SessionQueryErrorCode =
+  | 'SESSION_QUERY_ABORTED'
   | 'SESSION_QUERY_EVENT_NOT_FOUND'
+  | 'SESSION_QUERY_INDEX_FAILED'
   | 'SESSION_QUERY_INVALID_CONFIG'
+  | 'SESSION_QUERY_INVALID_CURSOR'
+  | 'SESSION_QUERY_INVALID_FILTER'
+  | 'SESSION_QUERY_INVALID_LIMIT'
+  | 'SESSION_QUERY_INVALID_QUERY'
   | 'SESSION_QUERY_INVALID_SURFACE'
   | 'SESSION_QUERY_INVALID_WINDOW'
   | 'SESSION_QUERY_PERSISTENCE_FAILED'
   | 'SESSION_QUERY_SESSION_NOT_FOUND'
+  | 'SESSION_QUERY_STALE_CURSOR'
   | 'SESSION_QUERY_SOURCE_CONFLICT'
 ```