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/test/context/scan/credentials.test.ts

@@ -9,7 +9,7 @@ import {
 } from '../../../src/context/scan/credentials.js';
 import type { KtxCredentialEnvelope, KtxScanReport, KtxScanWarning } from '../../../src/context/scan/types.js';
 
-describe('KTX scan credential redaction', () => {
+describe('ktx scan credential redaction', () => {
   it('keeps credential references inspectable', () => {
     const envReference: KtxCredentialEnvelope = { kind: 'env', name: 'DATABASE_URL' };
     const fileReference: KtxCredentialEnvelope = { kind: 'file', path: '~/.config/ktx/warehouse' };