feat: Add duckdb connector (#308)

* refactor(duckdb): extract shared json-safe bigint helper

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* feat(duckdb): add and register the duckdb primary connector

Add KtxDuckDbDialect, KtxDuckDbScanConnector (local file-backed, read-only,
never-create, main-schema introspection via information_schema and
duckdb_constraints() for foreign keys), and register the duckdb driver across
the dialect factory, driver registry, connection-type enum, warehouse descriptor,
config schema, scan normalization, connection test drivers, and status display.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* feat(duckdb): route live-database ingest through the DuckDB connector

Add the DuckDB live-database introspection bridge and dispatch duckdb
connections to it in local-adapters, matching the SQLite path. Repoint the
config-rejection test off duckdb (now a valid driver) onto the no-driver case.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* feat(duckdb): add duckdb to the setup database flow

Offer DuckDB in the interactive checklist and via ktx setup --database duckdb,
with a file-path prompt and duckdb-local default connection id, parallel to SQLite.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* feat(duckdb): attach native duckdb files in federation

Native .duckdb members ATTACH with (READ_ONLY) and no TYPE/INSTALL/LOAD, since
the duckdb format needs no extension. attachTypeForDriver returns null for the
native case; buildAttachStatements builds load statements from non-null types
only and emits a conditional ATTACH clause.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* docs(duckdb): document the duckdb primary-source connector

Add a DuckDB section to the primary-sources integration page (config, read-only
never-create behavior, main-schema scope, federation) and update the
supported-driver assertion in dialects.test.ts to include duckdb.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(duckdb): use single-namespace display shape for main-only refs

DuckDB v1 introspects the main schema and sets db=null on every table, so its
display refs are single-namespace like SQLite. The ansi shape emitted a 1-part
table display it then refused to parse, breaking column-level display resolution.
Switch the dialect to the sqlite display shape and add a round-trip test plus a
composite-foreign-key test that were missing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* refactor(duckdb): resolve connector dialect via getDialectForDriver

Route the connector's dialect through the shared factory like every other
connector, now that duckdb is registered. Single construction path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(duckdb): skip schema picker for single-file duckdb setup

DuckDB is a single-file, single-namespace ('main') database like SQLite,
but the setup scope step only skipped the schema picker for sqlite. DuckDB
fell into the multi-schema path with an empty schema list, rendering a
broken picker ("No matches found" for main). Extend the file-based-driver
early-return to cover duckdb so it ingests every table directly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* refactor(duckdb): reuse shared config helper and derive scope skip

Route duckdb path resolution through the shared resolveStringReference
helper instead of a local third copy of env:/file: handling. Derive the
setup scope-picker skip from SCOPE_DISCOVERY_SPECS membership rather than
a hardcoded sqlite/duckdb driver list.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* test(duckdb): use a genuinely unknown driver in the rejection test

The merged "rejects unknown drivers" test used `driver: duckdb` as its
unknown-driver stand-in, which stopped being unknown once this branch
added the duckdb connector. Switch to `nonsense` so it again exercises
the unsupported-driver config error.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* test(duckdb): cover dialect, connector, and live-introspection branches

Codecov flagged uncovered branches as dead code; all are real connector,
dialect, and live-ingest behavior. Add unit tests instead of removing them.

- dialect: precedence ladder, sample/clause builders, profiling expressions
- connector: url/env config forms, error throws, never-create guard,
  cardinality cap branches, table-scope empty/non-empty paths
- live-introspection: full-schema and table-scope extraction

Functions 100%, lines ~99% across the duckdb connector dir.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* docs: add DuckDB to supported-driver references

The DuckDB connector PR documented the connector itself but left the
scattered supported-driver enumerations stale. Add duckdb to the
federation concept page (participation table, activation, table naming,
limitations), the ktx setup CLI reference, the ktx.yaml warehouse-driver
table, the primary-sources field reference, and the quickstart driver
list (which also restores the missing ClickHouse entry).

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Andrey Avtomonov <andreybavt@gmail.com>

packages/cli/test/context/connections/dialects.test.ts

@@ -305,7 +305,7 @@ describe('getDialectForDriver', () => {
 
   it('throws with a supported-driver list for unknown drivers', () => {
     expect(() => getDialectForDriver('oracle')).toThrow(
-      'Unsupported driver "oracle". Supported drivers: bigquery, clickhouse, mongodb, mysql, postgres, snowflake, sqlite, sqlserver',
+      'Unsupported driver "oracle". Supported drivers: bigquery, clickhouse, duckdb, mongodb, mysql, postgres, snowflake, sqlite, sqlserver',
     );
   });
 

packages/cli/test/context/connections/drivers.test.ts

@@ -22,6 +22,7 @@ const connectionFixtures: Record<KtxConnectionDriver, FixtureFactory> = {
     schemas: ['public'],
   }),
   sqlite: () => ({ driver: 'sqlite', path: 'warehouse.db' }),
+  duckdb: (projectDir) => ({ driver: 'duckdb', path: join(projectDir, 'warehouse.duckdb') }),
   mongodb: () => ({
     driver: 'mongodb',
     url: 'mongodb://localhost:27017/app',
@@ -101,6 +102,7 @@ describe('driverRegistrations', () => {
     expect(listSupportedDrivers()).toEqual([
       'bigquery',
       'clickhouse',
+      'duckdb',
       'mongodb',
       'mysql',
       'postgres',
@@ -138,7 +140,7 @@ describe('driverRegistrations', () => {
     expect(connector.listTables).toEqual(expect.any(Function));
     await connector.cleanup?.();
 
-    if (registration.driver === 'sqlite') {
+    if (registration.driver === 'sqlite' || registration.driver === 'duckdb') {
       expect(registration.scopeConfigKey).toBeNull();
     } else {
       expect(registration.scopeConfigKey).not.toBeNull();

packages/cli/test/context/mcp/dialect-notes.test.ts

@@ -33,8 +33,7 @@ describe('per-dialect SQL notes', () => {
   });
 
   it('does not author notes for unreachable dialects', () => {
-    // duckdb/databricks appear in the resolver map but no connector produces them.
-    expect(DIALECTS_WITH_NOTES).not.toContain('duckdb');
+    // databricks appears in the resolver map but no connector produces it.
     expect(DIALECTS_WITH_NOTES).not.toContain('databricks');
   });