feat(capture): gate global hotkey on dictation readiness checklist

Stops the "stuck pill" failure where pressing the chord with missing
STT/LLM models triggers a recording that has nowhere to land. The
hotkey now stays disarmed until every gate (models downloaded, Input
Monitoring + Accessibility granted) is green; the empty-state checklist
in CapturesTab surfaces each unmet gate with a one-click action and
auto-arms the chord once everything turns green.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

backend/routes/captures.py

@@ -7,6 +7,8 @@ from fastapi.responses import FileResponse
 from sqlalchemy.orm import Session
 
 from .. import config, models
+from ..backends import get_llm_model_configs, get_stt_model_configs
+from ..backends.base import is_model_cached
 from ..database import Capture as DBCapture, get_db
 from ..services import captures as captures_service
 from ..services import settings as settings_service
@@ -152,6 +154,52 @@ async def refine_capture_endpoint(
     return capture
 
 
+@router.get("/capture/readiness", response_model=models.CaptureReadinessResponse)
+async def capture_readiness_endpoint(db: Session = Depends(get_db)):
+    """Whether the STT and LLM models the user has selected are downloaded.
+
+    The frontend gates the global hotkey on this — pressing the chord with
+    a missing model would otherwise produce a stuck "transcribing" pill that
+    waits forever for a download to finish. Checks on-disk cache, not RAM
+    load, so the answer survives backend restarts.
+    """
+    saved = settings_service.get_capture_settings(db)
+
+    stt_cfg = next(
+        (c for c in get_stt_model_configs() if c.model_size == saved.stt_model),
+        None,
+    )
+    llm_cfg = next(
+        (c for c in get_llm_model_configs() if c.model_size == saved.llm_model),
+        None,
+    )
+
+    if stt_cfg is None or llm_cfg is None:
+        # Should be impossible — both fields are pattern-validated against
+        # known sizes — but bail loudly rather than return half a response.
+        raise HTTPException(
+            status_code=500,
+            detail=f"No model config for stt={saved.stt_model} or llm={saved.llm_model}",
+        )
+
+    return models.CaptureReadinessResponse(
+        stt=models.ModelReadiness(
+            ready=is_model_cached(stt_cfg.hf_repo_id),
+            model_name=stt_cfg.model_name,
+            display_name=stt_cfg.display_name,
+            size=stt_cfg.model_size,
+            size_mb=stt_cfg.size_mb or None,
+        ),
+        llm=models.ModelReadiness(
+            ready=is_model_cached(llm_cfg.hf_repo_id),
+            model_name=llm_cfg.model_name,
+            display_name=llm_cfg.display_name,
+            size=llm_cfg.model_size,
+            size_mb=llm_cfg.size_mb or None,
+        ),
+    )
+
+
 @router.post("/captures/{capture_id}/retranscribe", response_model=models.CaptureResponse)
 async def retranscribe_capture_endpoint(
     capture_id: str,