feat: send_session_message 支持非 UTF-8 编码中文文件路径回退

Linux 环境下，当文件名包含非 UTF-8 编码的中文字符（如 GBK）
时，LLM 从 bash ls 输出获取的 UTF-8 路径无法匹配磁盘上的实
际字节，导致文件访问失败。

此提交新增 resolve_attachment_path() 函数，采用目录扫描+
多编码解码匹配策略：
1. 先按 UTF-8 原样访问（快速路径）
2. 失败后列出父目录，对每个文件尝试 UTF-8/GBK/lossy 解码
   与目标文件名比对，匹配成功则返回磁盘实际路径

同时修复 file_name 提取使用 to_string_lossy() 替代 to_str()
避免非 UTF-8 文件名静默丢失。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/tools/session_send.rs

@@ -180,25 +180,87 @@ fn validate_context(context: &ToolContext) -> anyhow::Result<()> {
 fn resolve_attachment_path(raw_path: &str) -> PathBuf {
     let path = Path::new(raw_path);
 
+    tracing::debug!(
+        raw_path = %raw_path,
+        raw_path_bytes = ?raw_path.as_bytes(),
+        "resolve_attachment_path: attempting to resolve path"
+    );
+
     // 1. 先按原样（UTF-8）尝试
     if path.exists() {
+        tracing::debug!(
+            raw_path = %raw_path,
+            "resolve_attachment_path: path exists as-is (UTF-8)"
+        );
         return path.to_path_buf();
     }
 
+    tracing::debug!(
+        raw_path = %raw_path,
+        "resolve_attachment_path: path not found as UTF-8, trying directory scan"
+    );
+
     // 2. 提取父目录和文件名，列出目录逐项比对
     if let (Some(parent), Some(target_filename)) = (path.parent(), path.file_name()) {
         let target_str = target_filename.to_string_lossy();
-        if let Ok(entries) = std::fs::read_dir(parent) {
+        tracing::debug!(
-            for entry in entries.flatten() {
+            parent = %parent.display(),
-                let entry_name = entry.file_name();
+            target_filename = %target_str,
-                if filename_matches_target(&entry_name, &target_str) {
+            target_filename_bytes = ?target_filename.as_encoded_bytes(),
-                    return entry.path();
+            "resolve_attachment_path: scanning parent directory"
+        );
+
+        match std::fs::read_dir(parent) {
+            Ok(entries) => {
+                let mut entry_count = 0;
+                for entry in entries.flatten() {
+                    entry_count += 1;
+                    let entry_name = entry.file_name();
+                    let is_match = filename_matches_target(&entry_name, &target_str);
+                    tracing::trace!(
+                        entry_path = %entry.path().display(),
+                        entry_name_lossy = %entry_name.to_string_lossy(),
+                        entry_name_bytes = ?entry_name.as_encoded_bytes(),
+                        is_match = is_match,
+                        "resolve_attachment_path: checking entry"
+                    );
+                    if is_match {
+                        tracing::debug!(
+                            entry_path = %entry.path().display(),
+                            entry_name_lossy = %entry_name.to_string_lossy(),
+                            "resolve_attachment_path: MATCH FOUND via encoding fallback"
+                        );
+                        return entry.path();
+                    }
                 }
+                tracing::debug!(
+                    parent = %parent.display(),
+                    entry_count = entry_count,
+                    "resolve_attachment_path: directory scan complete, no match"
+                );
+            }
+            Err(e) => {
+                tracing::warn!(
+                    parent = %parent.display(),
+                    error = %e,
+                    "resolve_attachment_path: failed to read directory"
+                );
             }
         }
+    } else {
+        tracing::debug!(
+            raw_path = %raw_path,
+            has_parent = path.parent().is_some(),
+            has_filename = path.file_name().is_some(),
+            "resolve_attachment_path: cannot extract parent or filename"
+        );
     }
 
     // 回退失败，返回原路径（让调用方报错）
+    tracing::warn!(
+        raw_path = %raw_path,
+        "resolve_attachment_path: all resolution attempts failed, returning original path"
+    );
     path.to_path_buf()
 }
 
@@ -210,25 +272,87 @@ fn filename_matches_target(on_disk_name: &std::ffi::OsStr, target: &str) -> bool
     use std::os::unix::ffi::OsStrExt;
     let bytes = on_disk_name.as_bytes();
 
-    // 直接 UTF-8 匹配（最快）
+    tracing::trace!(
-    if let Ok(decoded) = std::str::from_utf8(bytes) {
+        on_disk_bytes = ?bytes,
-        return decoded == target;
+        on_disk_bytes_hex = %format_bytes_hex(bytes),
+        target = %target,
+        "filename_matches_target: comparing"
+    );
+
+    // 直接 UTF-8 匹配
+    match std::str::from_utf8(bytes) {
+        Ok(decoded) => {
+            let matches = decoded == target;
+            tracing::trace!(
+                decoded_utf8 = %decoded,
+                matches = matches,
+                "filename_matches_target: UTF-8 decode result"
+            );
+            return matches;
+        }
+        Err(e) => {
+            tracing::trace!(
+                utf8_error = %e,
+                "filename_matches_target: not valid UTF-8, trying GBK"
+            );
+        }
     }
 
-    // 尝试 GBK/GB18030 解码
+    // 尝试 GBK 解码
     let (gbk_decoded, _, had_errors) = GBK.decode(bytes);
-    if !had_errors && gbk_decoded == target {
+    if !had_errors {
-        return true;
+        let matches = gbk_decoded == target;
+        tracing::debug!(
+            gbk_decoded = %gbk_decoded,
+            target = %target,
+            matches = matches,
+            gbk_decoded_bytes = ?gbk_decoded.as_bytes(),
+            target_bytes = ?target.as_bytes(),
+            "filename_matches_target: GBK decode result"
+        );
+        if matches {
+            return true;
+        }
+    } else {
+        tracing::debug!(
+            gbk_decoded_lossy = %gbk_decoded,
+            had_errors = had_errors,
+            "filename_matches_target: GBK decode had errors"
+        );
     }
 
-    // 回退：lossy 转换比对（处理非 GBK 编码）
+    // 回退：lossy 转换比对
     let lossy = String::from_utf8_lossy(bytes);
-    lossy == target
+    let matches = lossy == target;
+    tracing::debug!(
+        lossy = %lossy,
+        target = %target,
+        matches = matches,
+        "filename_matches_target: lossy fallback result"
+    );
+    matches
+}
+
+/// 将字节切片格式化为十六进制字符串，用于调试日志。
+#[cfg(unix)]
+fn format_bytes_hex(bytes: &[u8]) -> String {
+    bytes
+        .iter()
+        .map(|b| format!("{:02x}", b))
+        .collect::<Vec<_>>()
+        .join(" ")
 }
 
 #[cfg(not(unix))]
 fn filename_matches_target(on_disk_name: &std::ffi::OsStr, target: &str) -> bool {
-    on_disk_name.to_string_lossy() == target
+    let matches = on_disk_name.to_string_lossy() == target;
+    tracing::trace!(
+        on_disk_lossy = %on_disk_name.to_string_lossy(),
+        target = %target,
+        matches = matches,
+        "filename_matches_target (non-unix): comparing"
+    );
+    matches
 }
 
 fn parse_attachments(value: &serde_json::Value) -> anyhow::Result<Vec<MediaItem>> {