feat(tui): add HTTP client + daemon data models

- Add Go types matching daemon /queue response (QueueItem, QueueResponse)
- Add Go types for /status response (StatusResponse)
- Add HTTP client with configurable base URL (default http://127.0.0.1:4000)
- Add 1s timeout
- Add FetchQueue() ([]QueueItem, error)
- Add PostSkip() error
- Add PostNext() (string, error)
- Add GetPaneSessionMap() to parse pane_id→session_name map via tmux list-panes -a

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

tui/client.go

@@ -0,0 +1,170 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+const defaultDaemonURL = "http://127.0.0.1:4000"
+
+var httpClient = &http.Client{Timeout: 1 * time.Second}
+
+func daemonURL() string {
+	if u := os.Getenv("TRAILBOSS_URL"); u != "" {
+		return u
+	}
+	return defaultDaemonURL
+}
+
+// QueueItem represents a single stuck pane in the queue.
+// Matches the daemon's /queue response JOIN of queue + sessions.
+type QueueItem struct {
+	ID                int     `json:"id"`
+	SessionID         string  `json:"session_id"`
+	PaneID            string  `json:"pane_id"`
+	CWD               string  `json:"cwd"`
+	Reason            string  `json:"reason"`
+	LastMessage       *string `json:"last_message"` // nullable
+	StuckAt           int64   `json:"stuck_at"`     // epoch ms
+	SkipCooldownUntil *int64  `json:"skip_cooldown_until"` // nullable, epoch ms
+}
+
+// QueueResponse is the /queue endpoint response.
+type QueueResponse struct {
+	Items []QueueItem `json:"items"`
+	Count int         `json:"count"`
+}
+
+// StatusResponse is the /status endpoint response.
+// Matches daemon: { "status": "ok", "stuckCount": N }
+type StatusResponse struct {
+	Status    string `json:"status"`
+	StuckCount int   `json:"stuckCount"`
+}
+
+// NextResponse is the /next and /skip endpoint response.
+// Matches daemon: { "paneId": "...", "sessionId": "...", "reason": null | "..." }
+type NextResponse struct {
+	PaneID    *string `json:"paneId"`    // null if queue empty
+	SessionID *string `json:"sessionId"` // null if queue empty
+	Reason    *string `json:"reason"`    // null on success, error string if empty
+}
+
+// FetchQueue fetches the current queue from the daemon and returns the items.
+func FetchQueue() ([]QueueItem, error) {
+	resp, err := httpClient.Get(daemonURL() + "/queue")
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	var q QueueResponse
+	if err := json.NewDecoder(resp.Body).Decode(&q); err != nil {
+		return nil, err
+	}
+	return q.Items, nil
+}
+
+// FetchStatus fetches the daemon status.
+func FetchStatus() (StatusResponse, error) {
+	resp, err := httpClient.Get(daemonURL() + "/status")
+	if err != nil {
+		return StatusResponse{}, err
+	}
+	defer resp.Body.Close()
+
+	var s StatusResponse
+	if err := json.NewDecoder(resp.Body).Decode(&s); err != nil {
+		return StatusResponse{}, err
+	}
+	return s, nil
+}
+
+// PostSkip tells the daemon to skip the current queue head.
+func PostSkip() error {
+	resp, err := httpClient.Post(daemonURL()+"/skip", "application/json", nil)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	// Drain the response body but don't use it
+	_ = json.NewDecoder(resp.Body).Decode(&NextResponse{})
+	return nil
+}
+
+// PostNext fetches the head pane_id from the daemon.
+// Returns the pane ID string, or empty string if queue is empty (along with any error).
+func PostNext() (string, error) {
+	resp, err := httpClient.Get(daemonURL() + "/next")
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	var nr NextResponse
+	if err := json.NewDecoder(resp.Body).Decode(&nr); err != nil {
+		return "", err
+	}
+
+	// If paneId is null or reason indicates an error, return empty string
+	if nr.PaneID == nil || nr.Reason != nil && *nr.Reason != "" {
+		return "", nil
+	}
+
+	return *nr.PaneID, nil
+}
+
+// GetPaneSessionMap runs tmux list-panes and returns a map of pane_id → session_name.
+func GetPaneSessionMap() map[string]string {
+	out, err := exec.Command("tmux", "list-panes", "-a", "-F", "#{pane_id}:#{session_name}").Output()
+	if err != nil {
+		return map[string]string{}
+	}
+	m := make(map[string]string)
+	for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
+		parts := strings.SplitN(line, ":", 2)
+		if len(parts) == 2 {
+			m[parts[0]] = parts[1]
+		}
+	}
+	return m
+}
+
+// WritePreviewTarget writes paneID to /tmp/trailboss-preview-target so the
+// preview pane below the TUI mirrors that session.
+func WritePreviewTarget(paneID string) {
+	_ = os.WriteFile("/tmp/trailboss-preview-target", []byte(paneID), 0644)
+}
+
+// JumpToPane switches the tmux client to the given pane, recording the origin.
+func JumpToPane(paneID string) error {
+	// Resolve session name for the pane.
+	out, err := exec.Command("tmux", "display", "-p", "-t", paneID, "#{session_name}").Output()
+	if err != nil {
+		return fmt.Errorf("resolving session for pane %s: %w", paneID, err)
+	}
+	sessionName := strings.TrimSpace(string(out))
+	if sessionName == "" {
+		return fmt.Errorf("no session found for pane %s", paneID)
+	}
+
+	// Write origin before switching so prefix+B can return here.
+	if err := os.WriteFile("/tmp/trailboss-origin", []byte(paneID), 0644); err != nil {
+		// Non-fatal — log and continue.
+		_ = err
+	}
+
+	// Switch client to the target pane.
+	cmd := exec.Command("tmux",
+		"switch-client", "-t", sessionName, ";",
+		"select-window", "-t", paneID, ";",
+		"select-pane", "-t", paneID,
+	)
+	return cmd.Run()
+}