test: add core component requirements needed by the ported suite

The manifest declares dependencies: ["conversation"], and the ported tests
also exercise stt/tts. A full Home Assistant install resolves each core
component's own manifest.json requirements at runtime; bare pytest does not,
so CI failed with ModuleNotFoundError: No module named 'hassil' as soon as
entity.py's `from homeassistant.components import conversation` actually ran
(pythonpath fix in the prior commit got collection far enough to hit this).

Versions pinned to core tag 2026.9.2's own manifests:
homeassistant/components/conversation/manifest.json (hassil, gazetteer-matcher,
home-assistant-intents) and homeassistant/components/tts/manifest.json (mutagen).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01739Seac5eMAfNwFeiwV5r4

requirements_test.txt

@@ -1,3 +1,12 @@
 # Requires Python 3.14+ (Home Assistant 2026.9 floor). Not installable on Python 3.13.
 pytest-homeassistant-custom-component>=0.13.317
 openai==2.45.0
+
+# The manifest declares dependencies: ["conversation"], and the ported tests exercise
+# stt/tts too; a full HA install resolves each core component's own `requirements` at
+# runtime, but bare pytest does not, so they're pinned here to match core tag 2026.9.2's
+# homeassistant/components/{conversation,tts}/manifest.json.
+hassil==3.12.0
+gazetteer-matcher==1.1.0
+home-assistant-intents==2026.8.28
+mutagen==1.48.1