feat(fs): delegate win --server file reading to CM (#13736)

- Route Windows server-to-client file reads through CM instead of the connection layer
- Add FS IPC commands (ReadFile, CancelRead, SendConfirmForRead, ReadAllFiles) and CM data messages
  (ReadJobInitResult, FileBlockFromCM, FileReadDone, FileReadError, FileDigestFromCM, AllFilesResult)
- Track pending read validations and read jobs to coordinate CM-driven file transfers and clean them up
  on completion, cancellation, and errors
- Enforce a configurable file-transfer-max-files limit for ReadAllFiles and add stronger file name/path
  validation on the CM side
- Improve Flutter file transfer UX and robustness:
  - Use explicit percent/percentText progress fields
  - Derive speed and cancel actions from the active job
  - Handle job errors via FileModel.handleJobError and complete pending recursive tasks on failure
  - Wrap recursive directory operations in try/catch and await sendRemoveEmptyDir when removing empty directories

Signed-off-by: fufesou <linlong1266@gmail.com>

src/ipc.rs

@@ -112,6 +112,33 @@ pub enum FS {
         path: String,
         new_name: String,
     },
+    // CM-side file reading operations (Windows only)
+    // These enable Connection Manager to read files and stream them back to Connection
+    ReadFile {
+        path: String,
+        id: i32,
+        file_num: i32,
+        include_hidden: bool,
+        conn_id: i32,
+        overwrite_detection: bool,
+    },
+    CancelRead {
+        id: i32,
+        conn_id: i32,
+    },
+    SendConfirmForRead {
+        id: i32,
+        file_num: i32,
+        skip: bool,
+        offset_blk: u32,
+        conn_id: i32,
+    },
+    ReadAllFiles {
+        path: String,
+        id: i32,
+        include_hidden: bool,
+        conn_id: i32,
+    },
 }
 
 #[cfg(target_os = "windows")]
@@ -268,6 +295,72 @@ pub enum Data {
     #[cfg(windows)]
     ControlledSessionCount(usize),
     CmErr(String),
+    // CM-side file reading responses (Windows only)
+    // These are sent from CM back to Connection when CM handles file reading
+    /// Response to ReadFile: contains initial file list or error
+    ReadJobInitResult {
+        id: i32,
+        file_num: i32,
+        include_hidden: bool,
+        conn_id: i32,
+        /// Serialized protobuf bytes of FileDirectory, or error string
+        result: Result<Vec<u8>, String>,
+    },
+    /// File data block read by CM.
+    ///
+    /// The actual data is sent separately via `send_raw()` after this message to avoid
+    /// JSON encoding overhead for large binary data. This mirrors the `WriteBlock` pattern.
+    ///
+    /// **Protocol:**
+    /// - Sender: `send(FileBlockFromCM{...})` then `send_raw(data)`
+    /// - Receiver: `next()` returns `FileBlockFromCM`, then `next_raw()` returns data bytes
+    ///
+    /// **Note on empty data (e.g., empty files):**
+    /// Empty data is supported. The IPC connection uses `BytesCodec` with `raw=false` (default),
+    /// which prefixes each frame with a length header. So `send_raw(Bytes::new())` sends a
+    /// 1-byte frame (length=0), and `next_raw()` correctly returns an empty `BytesMut`.
+    /// See `libs/hbb_common/src/bytes_codec.rs` test `test_codec2` for verification.
+    FileBlockFromCM {
+        id: i32,
+        file_num: i32,
+        /// Data is sent separately via `send_raw()` to avoid JSON encoding overhead.
+        /// This field is skipped during serialization; sender must call `send_raw()` after sending.
+        /// Receiver must call `next_raw()` and populate this field manually.
+        #[serde(skip)]
+        data: bytes::Bytes,
+        compressed: bool,
+        conn_id: i32,
+    },
+    /// File read completed successfully
+    FileReadDone {
+        id: i32,
+        file_num: i32,
+        conn_id: i32,
+    },
+    /// File read failed with error
+    FileReadError {
+        id: i32,
+        file_num: i32,
+        err: String,
+        conn_id: i32,
+    },
+    /// Digest info from CM for overwrite detection
+    FileDigestFromCM {
+        id: i32,
+        file_num: i32,
+        last_modified: u64,
+        file_size: u64,
+        is_resume: bool,
+        conn_id: i32,
+    },
+    /// Response to ReadAllFiles: recursive directory listing
+    AllFilesResult {
+        id: i32,
+        conn_id: i32,
+        path: String,
+        /// Serialized protobuf bytes of FileDirectory, or error string
+        result: Result<Vec<u8>, String>,
+    },
     CheckHwcodec,
     #[cfg(feature = "flutter")]
     VideoConnCount(Option<usize>),