fix(stt,tts): restore mistralai — 2.4.8 is clean, ban lifted (#34841)

* docs(code-execution): document HERMES_* env narrowing + passthrough workaround

The execute_code sandbox-child env scrub (108397726, #27303) deliberately
dropped the broad HERMES_ prefix passthrough, keeping only an operational
4-var allowlist (HERMES_HOME/PROFILE/CONFIG/ENV). A script that relied on a
non-secret HERMES_* var (HERMES_BASE_URL, HERMES_KANBAN_DB, HERMES_*_WEBHOOK,
or a plugin-defined one) now sees it unset in the child.

Document the behavior change and the two recovery routes (terminal.env_passthrough
in config.yaml, or required_environment_variables in skill frontmatter), plus
the debug log line that surfaces the drop for diagnosis.

* fix(stt,tts): restore mistralai — 2.4.8 is clean, ban lifted

PyPI quarantined mistralai on 2026-05-12 after the malicious 2.4.6
release (Mini Shai-Hulud worm). 2.4.6 has since been removed from the
registry and clean releases resumed (2.4.7 2026-05-25, 2.4.8 2026-05-28).
This rolls back the blanket runtime ban so Voxtral STT + TTS work again,
following the restoration checklist the repo left in pyproject.toml.

Verified against the real SDK: 2.4.8 keeps the import path the code uses
(from mistralai.client import Mistral) and the audio.transcriptions.complete
/ audio.speech.complete surfaces.

Changes:
- pyproject.toml: re-add mistral extra pinned to mistralai==2.4.8; left
  OUT of [all] per the 2026-05-12 lazy-install policy (one quarantined
  release must not break fresh installs). uv.lock regenerated.
- tools/lazy_deps.py: add stt.mistral / tts.mistral entries so the SDK
  lazy-installs on first use (matches edge / elevenlabs).
- tools/transcription_tools.py: restore explicit-provider gate
  (_HAS_MISTRAL + key) and auto-detect entry (local>groq>openai>mistral>xai);
  _transcribe_mistral lazy-installs before import.
- tools/tts_tool.py: dispatcher routes back to _generate_mistral_tts;
  _import_mistral_client lazy-installs the SDK.
- hermes_cli/tools_config.py, hermes_cli/web_server.py: un-hide Mistral
  from the TTS provider picker and dashboard STT options.
- hermes_cli/security_advisories.py: KEEP the shai-hulud-2026-05 advisory
  (module policy forbids removal) — it is scoped to 2.4.6 only, so it
  still warns anyone with the poisoned build cached and never fires on
  2.4.8. Summary note updated to reflect the un-quarantine.
- tests: revert the disabled-behavior assertions added by the ban commit
  back to routing/positive expectations; add mistral to the
  lazy-installable-extras-excluded-from-[all] contract.

Reported by @SkYNewZ (#34503).

Validation: 189 targeted STT/TTS/lazy_deps/metadata tests pass; E2E with
the real mistralai 2.4.8 SDK routes both STT and TTS to mistral.

tests/tools/test_transcription_dotenv_fallback.py

@@ -99,12 +99,6 @@ class TestProviderSelectionGate:
             assert tt._get_provider({"enabled": True, "provider": "groq"}) == "groq"
 
     def test_explicit_mistral_sees_dotenv(self):
-        """Mistral STT is intentionally disabled (PyPI quarantine 2026-05-12).
-
-        Even with the dotenv key visible, explicit `provider: mistral` must
-        return "none" with a warning. Restore the previous behavior once
-        `mistralai` is un-quarantined on PyPI.
-        """
         from tools import transcription_tools as tt
 
         with patch.object(tt, "_HAS_FASTER_WHISPER", False), \
@@ -112,7 +106,7 @@ class TestProviderSelectionGate:
              patch.object(tt, "_has_local_command", return_value=False), \
              patch("hermes_cli.config.load_env",
                    return_value={"MISTRAL_API_KEY": "dotenv-secret"}):
-            assert tt._get_provider({"enabled": True, "provider": "mistral"}) == "none"
+            assert tt._get_provider({"enabled": True, "provider": "mistral"}) == "mistral"
 
     def test_explicit_xai_sees_dotenv(self):
         from tools import transcription_tools as tt