Add meeting capture with explicit start and stop (#253)

Maven can record a meeting when she is told to, transcribe it through the
STT she already has, and write a summary note. The audio lives in the blob
store #252 introduced, under the same retention loop.

Nothing here listens. Recorder.Append is the only way audio enters and it
refuses every frame unless someone explicitly started a session, so audio
arriving at an idle core is dropped rather than buffered. The plan document
asked for a keyword trigger ("maven record" heard in the room) and that is
refused: noticing a keyword means listening to the room, which is the one
behaviour this capability must not have.

Off unless configured twice over. No media block means nowhere to keep
audio, no capture block means no recorder, and in either case the four IPC
methods answer ErrUnknownMethod. On an unconfigured box there is no wire
path that begins a recording at all.

A forgotten session ends itself at max_minutes, checked on every append,
and the audio collected before the cap is kept. Stop with discard set is
what "забудь, не записывай" maps to and it leaves nothing behind. The
verbatim transcript is not saved unless save_transcript says so; the
summary is.

Long audio against n_ctx 4096 is handled by map-reduce over 3000-rune
windows rather than by truncation, because a truncated meeting summary
reads as complete and is not. Transcription is windowed at five minutes so
the whisper worker stays responsive to the voice path.

No second STT: internal/capture takes the stt.Transcriber the voice path
already holds. Capture with voice off is refused rather than degraded,
since hours of unreadable audio of other people is worse than no recording.

The three write methods are AuthWrite, not AuthStepUp: step-up needs a
passkey gesture the voice path cannot make, which would leave "запиши
встречу" impossible by voice. capture_status is AuthRead.

make build and make test both pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TrVSBKe3RFDF4fGYKWYQnX

internal/ipc/server.go

@@ -459,6 +459,20 @@ type Server struct {
 	// other CoreAPI implementation should have to carry it.
 	DescribeImageFn DescribeImageFunc
 
+	// Capture* — the meeting recorder (Vikunja #253). Set by the daemon only
+	// when a media store is configured AND capture.enabled is true; nil ⇒ all
+	// four methods answer ErrUnknownMethod. That is the load-bearing default for
+	// this capability: on an unconfigured box there is no wire path that begins a
+	// recording, so nothing can be recorded by accident, by a bug in a surface,
+	// or by a model deciding it would be helpful.
+	//
+	// They bypass CoreAPI because a recorder needs a blob store, an STT worker
+	// and a llama-server, none of which is a store operation.
+	CaptureStartFn  CaptureStartFunc
+	CaptureAppendFn CaptureAppendFunc
+	CaptureStopFn   CaptureStopFunc
+	CaptureStatusFn CaptureStatusFunc
+
 	// UnlockFn — unwraps the store encryption key from the wrapped blob using
 	// the passkey credential public key, opens the encrypted store, and wires
 	// the rest of the daemon (voice, loop, delivery). Set by the daemon when
@@ -489,6 +503,13 @@ type IngestMailFunc func(ctx context.Context, req IngestMailReq) (IngestMailResp
 // DescribeImageFunc — core-side image intake + description.
 type DescribeImageFunc func(ctx context.Context, req DescribeImageReq) (DescribeImageResp, error)
 
+// CaptureStartFunc / CaptureAppendFunc / CaptureStopFunc / CaptureStatusFunc —
+// the four core-side halves of the meeting recorder.
+type CaptureStartFunc func(ctx context.Context, req CaptureStartReq) (CaptureStartResp, error)
+type CaptureAppendFunc func(ctx context.Context, req CaptureAppendReq) (CaptureAppendResp, error)
+type CaptureStopFunc func(ctx context.Context, req CaptureStopReq) (CaptureStopResp, error)
+type CaptureStatusFunc func(ctx context.Context) (CaptureStatusResp, error)
+
 // CheckFunc — the auth hook signature. Wired by the daemon (auth.Gate.Check
 // satisfies this); dispatch calls it once per request after param-unmarshal
 // independence (it gets the raw params, may unmarshal what it needs — ipc
@@ -657,10 +678,11 @@ func withoutParams[R any](fn func(ctx context.Context, api CoreAPI) (R, error))
 // is still honored on the very next request with no extra plumbing here.
 //
 // MethodAssertStepUp, MethodStoreEncryptionKey, MethodUnlock,
-// MethodIngestMail, MethodSwapModel, MethodModelStatus and
-// MethodDescribeImage are NOT in this table: they bypass CoreAPI entirely
-// (s.StepUp / s.WrapKeyFn / s.UnlockFn / s.IngestMailFn / s.DescribeImageFn),
-// so dispatch special-cases them before consulting the table.
+// MethodIngestMail, MethodSwapModel, MethodModelStatus,
+// MethodDescribeImage and the four MethodCapture* methods are NOT in this
+// table: they bypass CoreAPI entirely (s.StepUp / s.WrapKeyFn / s.UnlockFn /
+// s.IngestMailFn / s.DescribeImageFn / s.Capture*Fn), so dispatch
+// special-cases them before consulting the table.
 var methodTable = map[Method]handlerFunc{
 	MethodWriteFact: withParams(func(ctx context.Context, api CoreAPI, p WriteFactReq) (idResp, error) {
 		id, err := api.WriteFact(ctx, p)
@@ -950,6 +972,58 @@ func (s *Server) dispatch(ctx context.Context, req Request) (json.RawMessage, er
 		}
 		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
 
+	case MethodCaptureStart:
+		if s.CaptureStartFn != nil {
+			var p CaptureStartReq
+			if err := unmarshalParams(req.Params, &p); err != nil {
+				return nil, err
+			}
+			resp, err := s.CaptureStartFn(ctx, p)
+			if err != nil {
+				return nil, err
+			}
+			return marshalResult(resp), nil
+		}
+		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
+
+	case MethodCaptureAppend:
+		if s.CaptureAppendFn != nil {
+			var p CaptureAppendReq
+			if err := unmarshalParams(req.Params, &p); err != nil {
+				return nil, err
+			}
+			resp, err := s.CaptureAppendFn(ctx, p)
+			if err != nil {
+				return nil, err
+			}
+			return marshalResult(resp), nil
+		}
+		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
+
+	case MethodCaptureStop:
+		if s.CaptureStopFn != nil {
+			var p CaptureStopReq
+			if err := unmarshalParams(req.Params, &p); err != nil {
+				return nil, err
+			}
+			resp, err := s.CaptureStopFn(ctx, p)
+			if err != nil {
+				return nil, err
+			}
+			return marshalResult(resp), nil
+		}
+		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
+
+	case MethodCaptureStatus:
+		if s.CaptureStatusFn != nil {
+			resp, err := s.CaptureStatusFn(ctx)
+			if err != nil {
+				return nil, err
+			}
+			return marshalResult(resp), nil
+		}
+		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
+
 	case MethodModelStatus:
 		if s.ModelStatusFn != nil {
 			resp, err := s.ModelStatusFn(ctx)