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.

scripts/ci-artifact-upload.test.mjs

@@ -20,8 +20,8 @@ async function readCiWorkflowOrSkip(testContext) {
   return readFile(ciWorkflowPath, 'utf-8');
 }
 
-describe('KTX CI artifact upload contract', () => {
-  it('uploads verified KTX package artifacts from the standalone check job', async (testContext) => {
+describe('ktx CI artifact upload contract', () => {
+  it('uploads verified ktx package artifacts from the standalone check job', async (testContext) => {
     const workflow = await readCiWorkflowOrSkip(testContext);
     if (workflow === null) {
       return;