feat(comment): db columns for comment suggestions (#315 phase 1)

Add suggested_text / suggestion_applied_at / suggestion_applied_by_id to the
comments table (migration) and mirror them in the hand-curated db.d.ts Comments
interface. suggested_text holds a proposed replacement for the comment's
anchored selection; the applied_* columns record who applied it and when.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/database/migrations/20260703T190000-comment-suggestions.ts

@@ -0,0 +1,26 @@
+import { type Kysely } from 'kysely';
+
+export async function up(db: Kysely<any>): Promise<void> {
+  // Agent comment suggestions (#315): a comment may carry a proposed replacement
+  // for its anchored `selection`, which a human applies via the comment UI.
+  await db.schema
+    .alterTable('comments')
+    // The proposed replacement text (plain text). NULL for ordinary comments.
+    .addColumn('suggested_text', 'text')
+    // When the suggestion was applied (NULL until applied).
+    .addColumn('suggestion_applied_at', 'timestamptz')
+    // Who applied it (NULL until applied).
+    .addColumn('suggestion_applied_by_id', 'uuid', (col) =>
+      col.references('users.id').onDelete('set null'),
+    )
+    .execute();
+}
+
+export async function down(db: Kysely<any>): Promise<void> {
+  await db.schema
+    .alterTable('comments')
+    .dropColumn('suggested_text')
+    .dropColumn('suggestion_applied_at')
+    .dropColumn('suggestion_applied_by_id')
+    .execute();
+}

apps/server/src/database/types/db.d.ts

@@ -173,6 +173,9 @@ export interface Comments {
   resolvedSource: string | null;
   selection: string | null;
   spaceId: string;
+  suggestedText: string | null;
+  suggestionAppliedAt: Timestamp | null;
+  suggestionAppliedById: string | null;
   type: string | null;
   updatedAt: Generated<Timestamp>;
   workspaceId: string;