Add file listing: share-dir flag, file_list_req/resp DataChannel messages

- proto: FileEntry, FileListResp types; MsgFileListReq/Resp msg types;
  CmdGetFileList + EvtFileList IPC types; Files field on IpcMessage
- mesh: ShareDir field + ScanShareDir(); on DataChannel open, auto-send
  MsgFileListReq to new peer; handle MsgFileListReq (scan + reply) and
  MsgFileListResp (emit EvtFileList to IPC subscribers)
- ipc: get_file_list command — own list returned immediately; remote peer
  list requested via DataChannel (response arrives as EvtFileList event)
- daemon: -share-dir flag wired to mesh.ShareDir
- test scripts: pass -share-dir /home/frejoh/Downloads/{alice,bob,charlie};
  test-network.sh verifies each peer's own file list via get_file_list
- FUTURE.md: document per-network share directories and multi-network design

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

internal/ipc/ipc.go

@@ -198,6 +198,26 @@ func handleClient(conn net.Conn, m *mesh.Mesh, anchorURL string, currentNetwork
 				Rooms:          []string{"general"},
 			})
 
+		case proto.CmdGetFileList:
+			if cmd.PeerID == nil || *cmd.PeerID == m.Identity.PeerID() {
+				// Local list — scan immediately.
+				send(proto.IpcMessage{
+					Type:   proto.EvtFileList,
+					PeerID: ptr(m.Identity.PeerID()),
+					Files:  m.ScanShareDir(),
+				})
+			} else {
+				// Remote list — send a request over the DataChannel.
+				// The response arrives as EvtFileList via the mesh event bus.
+				req, err := json.Marshal(proto.PeerMessage{Type: proto.MsgFileListReq})
+				if err != nil {
+					continue
+				}
+				if !m.SendTo(*cmd.PeerID, req) {
+					send(errMsg(fmt.Sprintf("get_file_list: peer %s not connected", (*cmd.PeerID).Short())))
+				}
+			}
+
 		case proto.CmdGenerateInvite:
 			net := currentNetwork()
 			if net == "" {

internal/mesh/mesh.go

@@ -3,6 +3,7 @@ package mesh
 
 import (
 	"log"
+	"os"
 	"sync"
 
 	"github.com/waste-go/internal/crypto"
@@ -22,6 +23,7 @@ type PeerConn struct {
 type Mesh struct {
 	Identity *crypto.Identity
 	Store    *store.Store // may be nil if persistence is disabled
+	ShareDir string       // directory whose contents are shared with peers; "" = no sharing
 
 	mu    sync.RWMutex
 	peers map[proto.PeerID]*PeerConn
@@ -41,6 +43,31 @@ func New(id *crypto.Identity, st *store.Store) *Mesh {
 	}
 }
 
+// ScanShareDir returns the list of files in the local share directory.
+// Returns an empty slice if ShareDir is unset or the directory is empty.
+func (m *Mesh) ScanShareDir() []proto.FileEntry {
+	if m.ShareDir == "" {
+		return nil
+	}
+	entries, err := os.ReadDir(m.ShareDir)
+	if err != nil {
+		log.Printf("mesh: scan share dir %s: %v", m.ShareDir, err)
+		return nil
+	}
+	var files []proto.FileEntry
+	for _, e := range entries {
+		if e.IsDir() {
+			continue
+		}
+		info, err := e.Info()
+		if err != nil {
+			continue
+		}
+		files = append(files, proto.FileEntry{Name: e.Name(), SizeBytes: info.Size()})
+	}
+	return files
+}
+
 // ── Peer management ───────────────────────────────────────────────────────────
 
 // AddPeer registers a connected peer and notifies subscribers.

internal/mesh/peer.go

@@ -56,6 +56,11 @@ func WireDataChannel(
 		}
 		m.AddPeer(peerConn)
 
+		// Request the peer's file list immediately after connect.
+		if req, err := json.Marshal(proto.PeerMessage{Type: proto.MsgFileListReq}); err == nil {
+			sendCh <- req
+		}
+
 		go func() {
 			for payload := range sendCh {
 				if err := dc.SendText(string(payload)); err != nil {
@@ -147,6 +152,28 @@ func handleDCMessage(data []byte, from proto.PeerID, localID *crypto.Identity, m
 
 func dispatchPeerMessage(msg proto.PeerMessage, from proto.PeerID, m *Mesh) {
 	switch msg.Type {
+	case proto.MsgFileListReq:
+		// Peer wants our file list — reply directly on their send channel.
+		files := m.ScanShareDir()
+		resp, err := json.Marshal(proto.PeerMessage{
+			Type:         proto.MsgFileListResp,
+			FileListResp: &proto.FileListResp{Files: files},
+		})
+		if err != nil {
+			return
+		}
+		m.SendTo(from, resp)
+
+	case proto.MsgFileListResp:
+		// Received a remote peer's file list — forward to IPC subscribers.
+		if msg.FileListResp != nil {
+			m.Emit(proto.IpcMessage{
+				Type:   proto.EvtFileList,
+				PeerID: peerIDPtr(from),
+				Files:  msg.FileListResp.Files,
+			})
+		}
+
 	case proto.MsgChat:
 		if msg.Chat != nil {
 			m.SaveMessage(msg.Chat)

internal/proto/proto.go

@@ -34,13 +34,15 @@ type PeerInfo struct {
 type MsgType string
 
 const (
-	MsgChat       MsgType = "chat"
-	MsgPeerGossip MsgType = "peer_gossip"
-	MsgFileOffer  MsgType = "file_offer"
-	MsgFileResp   MsgType = "file_response"
-	MsgFileDone   MsgType = "file_done"
-	MsgPing       MsgType = "ping"
-	MsgPong       MsgType = "pong"
+	MsgChat         MsgType = "chat"
+	MsgPeerGossip   MsgType = "peer_gossip"
+	MsgFileListReq  MsgType = "file_list_req"
+	MsgFileListResp MsgType = "file_list_resp"
+	MsgFileOffer    MsgType = "file_offer"
+	MsgFileResp     MsgType = "file_response"
+	MsgFileDone     MsgType = "file_done"
+	MsgPing         MsgType = "ping"
+	MsgPong         MsgType = "pong"
 )
 
 // PeerMessage is the top-level container sent over the "yaw" DataChannel.
@@ -49,12 +51,13 @@ type PeerMessage struct {
 	Type MsgType `json:"type"`
 
 	// Only one of these will be set, depending on Type.
-	Chat      *ChatMessage  `json:"chat,omitempty"`
-	Gossip    *PeerGossip   `json:"gossip,omitempty"`
-	FileOffer *FileOffer    `json:"file_offer,omitempty"`
-	FileResp  *FileResponse `json:"file_response,omitempty"`
-	FileDone  *FileDone     `json:"file_done,omitempty"`
-	Seq       *uint64       `json:"seq,omitempty"` // for ping/pong
+	Chat         *ChatMessage  `json:"chat,omitempty"`
+	Gossip       *PeerGossip   `json:"gossip,omitempty"`
+	FileListResp *FileListResp `json:"file_list_resp,omitempty"`
+	FileOffer    *FileOffer    `json:"file_offer,omitempty"`
+	FileResp     *FileResponse `json:"file_response,omitempty"`
+	FileDone     *FileDone     `json:"file_done,omitempty"`
+	Seq          *uint64       `json:"seq,omitempty"` // for ping/pong
 }
 
 // ChatMessage is a message to a room or a DM.
@@ -80,6 +83,18 @@ type GossipEntry struct {
 	LastSeen time.Time `json:"last_seen"`
 }
 
+// FileEntry describes a single file in a peer's shared directory.
+type FileEntry struct {
+	Name      string `json:"name"`
+	SizeBytes int64  `json:"size_bytes"`
+}
+
+// FileListResp is the payload for MsgFileListResp.
+// MsgFileListReq carries no payload — it is a zero-field request.
+type FileListResp struct {
+	Files []FileEntry `json:"files"`
+}
+
 // FileOffer initiates a file transfer.
 type FileOffer struct {
 	Mid       string `json:"mid"`        // dedup id
@@ -187,6 +202,7 @@ const (
 	CmdGetState     IpcMsgType = "get_state"
 	CmdSendFile      IpcMsgType = "send_file"
 	CmdGenerateInvite IpcMsgType = "generate_invite"
+	CmdGetFileList    IpcMsgType = "get_file_list"
 
 	// Events (daemon → UI)
 	EvtMessageReceived  IpcMsgType = "message_received"
@@ -198,6 +214,7 @@ const (
 	EvtStateSnapshot    IpcMsgType = "state_snapshot"
 	EvtError            IpcMsgType = "error"
 	EvtInviteGenerated  IpcMsgType = "invite_generated"
+	EvtFileList         IpcMsgType = "file_list"
 )
 
 // IpcMessage covers both commands and events.
@@ -229,4 +246,5 @@ type IpcMessage struct {
 	Rooms          []string     `json:"rooms,omitempty"`
 	ErrorMessage   string       `json:"error_message,omitempty"`
 	InviteString   string       `json:"invite,omitempty"`
+	Files          []FileEntry  `json:"files,omitempty"`
 }