feat(context): add driver-discriminated connection schemas (#96)

* refactor(context): export and describe mapping shape schemas

* feat(context): add driver-schemas module with warehouse drivers

* feat(context): add metabase, looker, lookml driver schemas with mappings

* feat(context): add notion, dbt, metricflow driver schemas

* refactor(context): make connectionSchema a driver-discriminated union

* chore(context): re-export KtxConnectionConfig from project package

* docs(context): add connection driver schema plan

* chore(secrets): allowlist example credentials in driver-schemas fixtures

* test(cli): align metabase fixtures with required api_url field

The driver-discriminated union added in this branch now requires api_url
for metabase connections and a known driver for warehouses. Update slow
CLI test fixtures and assertions so they exercise the new schema:
- ingest.test-utils.ts: add api_url to the prod-metabase fixture.
- setup.test.ts: switch metabase fixture from 'url' to 'api_url'.
- local-scan-connectors.test.ts: invalid-driver/missing-driver tests now
  expect the schema error from loadKtxProject (parse-time rejection).

packages/context/src/ingest/adapters/metabase/local-source-state-store.test.ts

@@ -3,6 +3,7 @@ import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 import { afterEach, beforeEach, describe, expect, it } from 'vitest';
 import { buildDefaultKtxProjectConfig } from '../../../project/index.js';
+import { connectionConfigSchema } from '../../../project/driver-schemas.js';
 import { KtxYamlMetabaseSourceStateReader, LocalMetabaseDiscoveryCache } from './local-source-state-store.js';
 
 describe('Metabase YAML source state and discovery cache', () => {
@@ -23,10 +24,11 @@ describe('Metabase YAML source state and discovery cache', () => {
       config: {
         ...buildDefaultKtxProjectConfig(),
         connections: {
-          'prod-metabase': {
+          'prod-metabase': connectionConfigSchema.parse({
             driver: 'metabase',
+            api_url: 'https://metabase.example.com',
             mappings,
-          },
+          }),
         },
       },
     };

packages/context/src/ingest/local-mapping-reconcile.test.ts

@@ -27,11 +27,12 @@ describe('local mapping yaml reconciliation bridge', () => {
     const project = projectWithConnections({
       'prod-metabase': {
         driver: 'metabase',
+        api_url: 'https://metabase.example.com',
         mappings: {
           databaseMappings: { '1': 'prod-warehouse' },
           syncEnabled: { '1': true },
           syncMode: 'ONLY',
-          selections: { collections: [12] },
+          selections: { collections: [12], items: [] },
           defaultTagNames: ['ktx'],
         },
       },
@@ -46,6 +47,8 @@ describe('local mapping yaml reconciliation bridge', () => {
     const project = projectWithConnections({
       'prod-looker': {
         driver: 'looker',
+        base_url: 'https://looker.example.com',
+        client_id: 'client',
         mappings: { connectionMappings: { analytics: 'prod-warehouse' } },
       },
       'prod-warehouse': { driver: 'postgres', url: 'postgresql://readonly@db.test/analytics' },