fix(security): skip symlinks in all filepath.Walk callbacks (M1)

filepath.Walk uses Lstat internally and does NOT descend into
symlinked directories. However, symlink entries are still passed
to the walk callback — appearing as files in results. Since H1
fixed all file opens to use O_NOFOLLOW, these symlink paths are
unreadable dead ends that leak path information.

Fix: add info.Mode()&os.ModeSymlink check at the top of every
walk callback across the codebase:

  file_tool.go       — searchContent, searchFiles name match,
                       glob with path separators
  perf_tools.go      — multiGrep
  resource.go        — FileResolver.walkAndMatch

All five walks now silently skip symlink entries. This is
defense-in-depth: O_NOFOLLOW on opens was the primary fix,
skipping symlinks at the walk level prevents path disclosure
and eliminates any TOCTOU concern entirely.

Fixes M1 from security audit.

Author: molty3000

cmd/odek/file_tool.go

@@ -380,6 +380,11 @@ func (t *searchFilesTool) searchContent(args searchFilesArgs) (string, error) {
 			}
 			return nil
 		}
+		// Skip symlinks — prevents TOCTOU on the path and avoids listing
+		// files the agent can't read (O_NOFOLLOW opens would fail anyway).
+		if info.Mode()&os.ModeSymlink != 0 {
+			return nil
+		}
 
 		// Apply file_glob filter
 		if args.FileGlob != "" {
@@ -474,6 +479,10 @@ func (t *searchFilesTool) searchFiles(args searchFilesArgs) (string, error) {
 				}
 				return nil
 			}
+			// Skip symlinks — prevents listing files the agent can't read.
+			if info.Mode()&os.ModeSymlink != 0 {
+				return nil
+			}
 			match, _ := filepath.Match(pattern, info.Name())
 			if match {
 				matches = append(matches, searchMatch{Path: path})
@@ -1034,6 +1043,11 @@ func (t *globTool) Call(argsJSON string) (result string, err error) {
 			if err != nil || info == nil {
 				return nil
 			}
+			// Skip symlinks — prevents traversal via symlinked directories
+			// and avoids listing files the agent can't read.
+			if info.Mode()&os.ModeSymlink != 0 {
+				return nil
+			}
 			match, _ := filepath.Match(args.Pattern, path)
 			if !match {
 				// Also try relative to root

cmd/odek/perf_tools.go

@@ -1091,6 +1091,10 @@ func (t *multiGrepTool) searchPattern(pattern, root, fileGlob string, limit int)
 			}
 			return nil
 		}
+		// Skip symlinks — prevents TOCTOU and listing unreadable files.
+		if info.Mode()&os.ModeSymlink != 0 {
+			return nil
+		}
 		if fileGlob != "" {
 			match, _ := filepath.Match(fileGlob, info.Name())
 			if !match {

internal/resource/resource.go

@@ -289,6 +289,11 @@ func (f *FileResolver) walkAndMatch(searchTerm string) []string {
 		if err != nil {
 			return nil
 		}
+		// Skip symlinks — resource resolver uses O_NOFOLLOW on Load,
+		// so symlinks are unreadable anyway.
+		if info.Mode()&os.ModeSymlink != 0 {
+			return nil
+		}
 		if info.IsDir() {
 			if skipDir(info.Name()) {
 				return filepath.SkipDir