feat(import): auto-generate session index after all import paths

Session index (segment/message_context tables) was previously generated
inconsistently: CLI used postImportHook, Desktop relied on a separate
explicit RPC call, and the CLI sync/pull legacy importer never built it.

Move generateSessionIndex / generateIncrementalSessionIndex into the
shared importers (streaming-importer.ts, incremental-importer.ts) so
every caller gets it automatically. Remove the now-redundant calls from
CLI's postImportHook. Also add the calls to the legacy importer.ts used
by CLI sync/pull, which had no session index at all.

Incremental imports use generateIncrementalSessionIndex, which preserves
existing AI summaries. Full imports call generateSessionIndex only on
newly created sessions where no summaries exist.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/node-runtime/src/import/incremental-importer.ts

@@ -9,7 +9,7 @@
  */
 
 import type { DatabaseAdapter } from '@openchatlab/core'
-import { generateMessageKey } from '@openchatlab/core'
+import { generateMessageKey, generateIncrementalSessionIndex } from '@openchatlab/core'
 import { streamParseFile, detectFormat, type ParseProgress } from '@openchatlab/parser'
 import { insertFtsEntries, hasFtsTable } from '../fts'
 import type { ImportProgressCallback } from './streaming-importer'
@@ -379,6 +379,15 @@ export async function incrementalImport(
       }
     }
 
+    // Incremental session index (segment / message_context tables)
+    if (newMessageCount > 0) {
+      try {
+        generateIncrementalSessionIndex(db)
+      } catch {
+        /* non-fatal */
+      }
+    }
+
     const sessionStats = db
       .prepare(
         `SELECT

packages/node-runtime/src/import/streaming-importer.ts

@@ -10,7 +10,7 @@
  */
 
 import type { DatabaseAdapter } from '@openchatlab/core'
-import { CHAT_DB_INDEXES } from '@openchatlab/core'
+import { CHAT_DB_INDEXES, generateSessionIndex } from '@openchatlab/core'
 import type { ParsedMember, ParsedMessage } from '@openchatlab/shared-types'
 import {
   streamParseFile,
@@ -518,6 +518,14 @@ async function streamImportSingle(
     doCheckpoint()
     logger?.perf('WAL checkpoint done', totalMessageCount)
 
+    // Build session index (segment / message_context tables)
+    try {
+      generateSessionIndex(db)
+      logger?.perf('Session index built', totalMessageCount)
+    } catch {
+      /* non-fatal */
+    }
+
     // Post-import hook (e.g. overview cache)
     try {
       await deps.postImportHook?.(db, sessionId)