refactor(context): validate ktx.yaml with Zod and surface issues in status

- Replace hand-rolled ktx.yaml parsing with a strict Zod schema and
  derive KtxProjectConfig types from it.
- Add validateKtxProjectConfig returning structured KtxConfigIssue[]
  with migration hints for deprecated keys (ingest.llm,
  scan.enrichment.backend, etc.).
- Wire ktx status/doctor to run validation, render schema issues in
  plain and JSON output, and add a Config row to project status.
- Update the orbit example to camelCase scan.relationships keys to
  match the schema.

scripts/examples-docs.test.mjs

@@ -50,8 +50,8 @@ describe('standalone example docs', () => {
       config,
       /path: \.\.\/\.\.\/packages\/context\/test\/fixtures\/relationship-benchmarks\/orbit_style_product_no_declared_constraints\/data\.sqlite/,
     );
-    assert.match(config, /llm_proposals: false/);
-    assert.match(config, /validation_required_for_manifest: true/);
+    assert.match(config, /llmProposals: false/);
+    assert.match(config, /validationRequiredForManifest: true/);
   });
 
   it('documents the Postgres historic SQL smoke example', async () => {