feat(settings): ambient_mode and ambient_cadence_secs fields

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/settings/settings.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"strconv"
 )
 
 // ErrInvalidBackend marks a settings value whose ai_backend is not a known
@@ -16,13 +17,36 @@ import (
 // without importing the ai package.
 var ErrInvalidBackend = errors.New("settings: invalid ai backend")
 
+// ErrInvalidAmbientMode marks a settings value whose ambient_mode is not a
+// known mode. The applier returns it (wrapped) so the HTTP layer can map it to
+// 400 without importing the ambient package.
+var ErrInvalidAmbientMode = errors.New("settings: invalid ambient mode")
+
+// Ambient mode dial values.
+const (
+	AmbientOff    = "off"
+	AmbientStatus = "status"
+	AmbientNotify = "notify"
+)
+
+// ValidAmbientMode reports whether m is a known ambient mode constant.
+func ValidAmbientMode(m string) bool {
+	switch m {
+	case AmbientOff, AmbientStatus, AmbientNotify:
+		return true
+	}
+	return false
+}
+
 // Settings is the user-editable configuration. Field names mirror the env vars
 // they replace: KEEL_AI_BACKEND, KEEL_MARVIN_CMD, KEEL_KNOWLEDGE_FILE, KEEL_AW_URL.
 type Settings struct {
-	AIBackend     string `json:"ai_backend"`
-	MarvinCmd     string `json:"marvin_cmd"`
-	KnowledgePath string `json:"knowledge_path"`
-	AWURL         string `json:"aw_url"`
+	AIBackend          string `json:"ai_backend"`
+	MarvinCmd          string `json:"marvin_cmd"`
+	KnowledgePath      string `json:"knowledge_path"`
+	AWURL              string `json:"aw_url"`
+	AmbientMode        string `json:"ambient_mode"`
+	AmbientCadenceSecs int    `json:"ambient_cadence_secs"`
 }
 
 // DefaultPath returns ~/.keel/settings.json.
@@ -77,10 +101,22 @@ func SeedFromEnv() Settings {
 	if awURL == "" {
 		awURL = "http://localhost:5600"
 	}
+	ambientMode := os.Getenv("KEEL_AMBIENT_MODE")
+	if ambientMode == "" {
+		ambientMode = AmbientNotify
+	}
+	ambientCadenceSecs := 300
+	if v := os.Getenv("KEEL_AMBIENT_CADENCE_SECS"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil && n > 0 {
+			ambientCadenceSecs = n
+		}
+	}
 	return Settings{
-		AIBackend:     backend,
-		MarvinCmd:     os.Getenv("KEEL_MARVIN_CMD"),
-		KnowledgePath: os.Getenv("KEEL_KNOWLEDGE_FILE"),
-		AWURL:         awURL,
+		AIBackend:          backend,
+		MarvinCmd:          os.Getenv("KEEL_MARVIN_CMD"),
+		KnowledgePath:      os.Getenv("KEEL_KNOWLEDGE_FILE"),
+		AWURL:              awURL,
+		AmbientMode:        ambientMode,
+		AmbientCadenceSecs: ambientCadenceSecs,
 	}
 }