Fix filing taxonomy schema mismatch by adding explicit column verification

The filing_taxonomy_snapshot table was missing parser_engine and related columns
on databases created before the taxonomy surface sidecar migration. This caused
filing sync workflows to fail with 'table has no column named parser_engine'.

Changes:
- Add TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS constant for required columns
- Add verifyCriticalSchema() to fail fast at startup if schema is incompatible
- Reorder ensureTaxonomySnapshotCompat to check table existence before column ops
- Add explicit column verification after ALTER TABLE attempts
- Add regression tests for missing column detection

Fixes #2

lib/server/db/index.ts

@@ -11,7 +11,8 @@ import { schema } from './schema';
 import {
   ensureLocalSqliteSchema,
   hasColumn,
-  hasTable
+  hasTable,
+  TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS
 } from './sqlite-schema-compat';
 
 type AppDrizzleDb = ReturnType<typeof createDb>;
@@ -132,6 +133,27 @@ function ensureSearchVirtualTables(client: Database) {
   client.exec('CREATE INDEX IF NOT EXISTS `search_chunk_vec_lookup_idx` ON `search_chunk_vec` (`scope`, `user_id`, `source_kind`, `ticker`);');
 }
 
+function verifyCriticalSchema(client: Database) {
+  if (!hasTable(client, 'filing_taxonomy_snapshot')) {
+    return;
+  }
+
+  const missingColumns: string[] = [];
+  for (const columnName of TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS) {
+    if (!hasColumn(client, 'filing_taxonomy_snapshot', columnName)) {
+      missingColumns.push(columnName);
+    }
+  }
+
+  if (missingColumns.length > 0) {
+    throw new Error(
+      `[db] CRITICAL: Database schema is incompatible. ` +
+        `filing_taxonomy_snapshot is missing columns: ${missingColumns.join(', ')}. ` +
+        `Delete the database file and restart to rebuild schema.`
+    );
+  }
+}
+
 export function getSqliteClient() {
   if (!globalThis.__fiscalSqliteClient) {
     configureCustomSqliteRuntime();
@@ -147,6 +169,7 @@ export function getSqliteClient() {
     client.exec('PRAGMA busy_timeout = 5000;');
     loadSqliteExtensions(client);
     ensureLocalSqliteSchema(client);
+    verifyCriticalSchema(client);
     ensureFinancialIngestionSchemaHealthy(client, {
       mode: resolveFinancialSchemaRepairMode(process.env.FINANCIAL_SCHEMA_REPAIR_MODE)
     });
@@ -176,5 +199,6 @@ export const __dbInternals = {
   hasColumn,
   hasTable,
   isVectorExtensionLoaded,
-  loadSqliteExtensions
+  loadSqliteExtensions,
+  verifyCriticalSchema
 };