feat: implement agent-notify CLI with hooks and tmux passthrough

Add OSC 777 notification sender, Cursor/Claude hook adapters,
config/install commands, and README for Ghostty + tmux setup.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/hook/claude.go

@@ -0,0 +1,41 @@
+package hook
+
+import (
+	"encoding/json"
+	"io"
+
+	"github.com/longbin/agent-notify/internal/config"
+	"github.com/longbin/agent-notify/internal/context"
+	"github.com/longbin/agent-notify/internal/notify"
+)
+
+type claudePayload struct {
+	StopHookActive bool   `json:"stop_hook_active"`
+	Message        string `json:"message"`
+}
+
+type claudeResponse struct {
+	TerminalSequence string `json:"terminalSequence,omitempty"`
+}
+
+func RunClaude(r io.Reader, cfg config.Config, event string, w io.Writer) error {
+	if !cfg.EventEnabled(event) {
+		_, err := io.WriteString(w, "{}\n")
+		return err
+	}
+	var payload claudePayload
+	_ = json.NewDecoder(r).Decode(&payload)
+	if event == "stop" && payload.StopHookActive {
+		_, err := io.WriteString(w, "{}\n")
+		return err
+	}
+
+	meta := context.MetaFromEnv("Claude", event)
+	title := context.Render(cfg.Notify.TitleTemplate, meta)
+	body := cfg.BodyForEvent(event)
+	seq := notify.BuildSequence(cfg.Notify.Protocol, title, body)
+	resp := claudeResponse{TerminalSequence: seq}
+	enc := json.NewEncoder(w)
+	enc.SetEscapeHTML(false)
+	return enc.Encode(resp)
+}