feat(examples): ship the §11 golden fixtures with byte-exact conformance

TDD step 8: three golden cases per the §11 format (manifest.json,
fixture/, ingested-at.txt, expected-bundle/) — ingest-golden-file and
ingest-golden-sql are the conformance MUSTs; ingest-golden-http
documents and exercises the optional extension against mock payloads.
The conformance test re-materializes each case into a fresh directory
and compares byte for byte; offline and credential-free (the sql
fixture is a committed database file, http never opens a socket).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QeqhJpYQyghASjiJo5EhGg

examples/ingest-golden-http/expected-bundle/index.md

@@ -0,0 +1,2 @@
+Golden http-source bundle: a status payload fetched from a mock endpoint.
+- [Status](ingest-status.md)

examples/ingest-golden-http/expected-bundle/ingest-status.md

@@ -0,0 +1,13 @@
+---
+type: dataset
+title: Status
+source_system: golden-api
+source_query: /status.json
+ingested_at: 2026-07-16T12:00:00Z
+ingest_manifest: manifest@826dbd7dec4d4c79
+generated: true
+---
+
+```
+{"status": "ok", "count": 3}
+```