fix: handle bare path strings in files_modified/files_read columns (#1359)

JSON.parse('/path/to/file') throws SyntaxError, crashing the viewer and
any code reading observations with legacy bare-path data in those columns.

- Add parseFileList() helper in observations/files.ts — tries JSON.parse,
  falls back to wrapping bare strings in an array
- Replace unsafe JSON.parse calls in files.ts, SessionStore.ts, ChromaSync.ts
- Add 9 unit tests covering null, empty, valid JSON, bare paths, invalid JSON

Closes #1359

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

src/services/sqlite/SessionStore.ts

@@ -14,6 +14,7 @@ import {
 } from '../../types/database.js';
 import type { PendingMessageStore } from './PendingMessageStore.js';
 import { computeObservationContentHash, findDuplicateObservation } from './observations/store.js';
+import { parseFileList } from './observations/files.js';
 
 /**
  * Session data store for SDK sessions, observations, and summaries
@@ -1307,20 +1308,10 @@ export class SessionStore {
 
     for (const row of rows) {
       // Parse files_read
-      if (row.files_read) {
-        const files = JSON.parse(row.files_read);
-        if (Array.isArray(files)) {
-          files.forEach(f => filesReadSet.add(f));
-        }
-      }
+      parseFileList(row.files_read).forEach(f => filesReadSet.add(f));
 
       // Parse files_modified
-      if (row.files_modified) {
-        const files = JSON.parse(row.files_modified);
-        if (Array.isArray(files)) {
-          files.forEach(f => filesModifiedSet.add(f));
-        }
-      }
+      parseFileList(row.files_modified).forEach(f => filesModifiedSet.add(f));
     }
 
     return {

src/services/sqlite/observations/files.ts

@@ -7,6 +7,21 @@ import { Database } from 'bun:sqlite';
 import { logger } from '../../../utils/logger.js';
 import type { SessionFilesResult } from './types.js';
 
+/**
+ * Safely parse a JSON array string from the DB.
+ * Handles legacy bare-path strings (e.g. "/foo/bar.ts") by wrapping them
+ * in an array instead of crashing with a SyntaxError (fix for #1359).
+ */
+export function parseFileList(value: string | null | undefined): string[] {
+  if (!value) return [];
+  try {
+    const parsed = JSON.parse(value);
+    return Array.isArray(parsed) ? parsed : [String(parsed)];
+  } catch {
+    return [value];
+  }
+}
+
 /**
  * Get aggregated files from all observations for a session
  */
@@ -30,20 +45,10 @@ export function getFilesForSession(
 
   for (const row of rows) {
     // Parse files_read
-    if (row.files_read) {
-      const files = JSON.parse(row.files_read);
-      if (Array.isArray(files)) {
-        files.forEach(f => filesReadSet.add(f));
-      }
-    }
+    parseFileList(row.files_read).forEach(f => filesReadSet.add(f));
 
     // Parse files_modified
-    if (row.files_modified) {
-      const files = JSON.parse(row.files_modified);
-      if (Array.isArray(files)) {
-        files.forEach(f => filesModifiedSet.add(f));
-      }
-    }
+    parseFileList(row.files_modified).forEach(f => filesModifiedSet.add(f));
   }
 
   return {