fix: exclude primary key index from unique constraint check in migration 7 (#1771)

* fix: exclude primary key index from unique constraint check in migration 7

PRAGMA index_list returns all indexes including those backing PRIMARY KEY
columns (origin='pk'), which always have unique=1. The check was therefore
always true, causing migration 7 to run the full DROP/CREATE/RENAME table
sequence on every worker startup instead of short-circuiting once the
UNIQUE constraint had already been removed.

Fix: filter to non-PK indexes by requiring idx.origin !== 'pk'. The
origin field is already present on the existing IndexInfo interface.

Fixes #1749

* fix: apply pk-origin guard to all three migration code paths

CodeRabbit correctly identified that the origin !== 'pk' fix was only
applied to MigrationRunner.ts but not to the two other active code paths
that run the same removeSessionSummariesUniqueConstraint logic:

- SessionStore.ts:220 — used by DatabaseManager and worker-service
- plugin/scripts/context-generator.cjs — bundled artifact (minified)

All three paths now consistently exclude primary-key indexes when
detecting unique constraints on session_summaries.

src/services/sqlite/SessionStore.ts

@@ -217,7 +217,7 @@ export class SessionStore {
   private removeSessionSummariesUniqueConstraint(): void {
     // Check actual constraint state — don't rely on version tracking alone (issue #979)
     const summariesIndexes = this.db.query('PRAGMA index_list(session_summaries)').all() as IndexInfo[];
-    const hasUniqueConstraint = summariesIndexes.some(idx => idx.unique === 1);
+    const hasUniqueConstraint = summariesIndexes.some(idx => idx.unique === 1 && idx.origin !== 'pk');
 
     if (!hasUniqueConstraint) {
       // Already migrated (no constraint exists)

src/services/sqlite/migrations/runner.ts

@@ -189,7 +189,7 @@ export class MigrationRunner {
   private removeSessionSummariesUniqueConstraint(): void {
     // Check actual constraint state — don't rely on version tracking alone (issue #979)
     const summariesIndexes = this.db.query('PRAGMA index_list(session_summaries)').all() as IndexInfo[];
-    const hasUniqueConstraint = summariesIndexes.some(idx => idx.unique === 1);
+    const hasUniqueConstraint = summariesIndexes.some(idx => idx.unique === 1 && idx.origin !== 'pk');
 
     if (!hasUniqueConstraint) {
       // Already migrated (no constraint exists)