refactor: enforce ktx naming and AGENTS.md compliance sweep (#289)

Align the tree with AGENTS.md/CLAUDE.md conventions:

- Rewrite user-facing strings, docs, and tests to lowercase `ktx`
  (no bare uppercase `KTX` tokens remain outside literal identifiers).
- Drop the legacy `historicSql` migration path and its now-unused
  helpers, per the no-backward-compat rule.
- Remove `as unknown as` / `any` casts: narrow `BaseTool` generics to
  `z.ZodObject`, add a typed `createLookerClient`, and delete the dead
  `getParametersSchema`/`toAnthropicFormat` pre-AI-SDK helpers.
- Use `InvalidArgumentError` for Commander parse failures.
- Finish the adapter→connector prose conversion in the `ktx.yaml` docs
  while keeping the literal `adapters` config key.

packages/cli/src/source-mapping.ts

@@ -54,9 +54,7 @@ async function createDefaultLookerClient(
       return lookerCredentialsFromLocalConnection(lookerConnectionId, project.config.connections[lookerConnectionId]);
     },
   });
-  return factory.createClient(connectionId) as unknown as Pick<LookerMappingClient, 'listLookerConnections'> & {
-    cleanup?(): Promise<void>;
-  };
+  return factory.createLookerClient(connectionId);
 }
 
 function isLookerConnection(project: KtxLocalProject, connectionId: string): boolean {