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/prepare-cli-bin.mjs

@@ -36,7 +36,7 @@ export async function ensureCliBinExecutable(rootDir = ktxRootDir()) {
 if (import.meta.url === pathToFileURL(process.argv[1]).href) {
   try {
     const binPath = await ensureCliBinExecutable();
-    process.stdout.write(`Prepared KTX CLI bin: ${binPath}\n`);
+    process.stdout.write(`Prepared ktx CLI bin: ${binPath}\n`);
   } catch (error) {
     process.stderr.write(`${error instanceof Error ? error.message : String(error)}\n`);
     process.exitCode = 1;