fix: follow symlinks when discovering project directories

os.ReadDir returns DirEntry where IsDir() is false for symlinks to
directories. This caused DiscoverClaudeProjects and the Gemini
discovery functions to silently skip symlinked project directories,
making CLAUDE_PROJECTS_DIR unusable with symlinked repos.

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

Author: clkao

internal/sync/discovery.go

@@ -20,6 +20,12 @@ var uuidRe = regexp.MustCompile(
 		`[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12})$`,
 )
 
+// isDirOrSymlink reports whether the entry is a directory or a
+// symlink (which may point to a directory).
+func isDirOrSymlink(entry os.DirEntry) bool {
+	return entry.IsDir() || entry.Type()&os.ModeSymlink != 0
+}
+
 // DiscoveredFile holds a discovered session JSONL file.
 type DiscoveredFile struct {
 	Path    string
@@ -37,7 +43,7 @@ func DiscoverClaudeProjects(projectsDir string) []DiscoveredFile {
 
 	var files []DiscoveredFile
 	for _, entry := range entries {
-		if !entry.IsDir() {
+		if !isDirOrSymlink(entry) {
 			continue
 		}
 
@@ -271,7 +277,7 @@ func DiscoverGeminiSessions(
 
 	var files []DiscoveredFile
 	for _, hd := range hashDirs {
-		if !hd.IsDir() {
+		if !isDirOrSymlink(hd) {
 			continue
 		}
 		hash := hd.Name()
@@ -326,7 +332,7 @@ func FindGeminiSourceFile(
 	}
 
 	for _, hd := range hashDirs {
-		if !hd.IsDir() {
+		if !isDirOrSymlink(hd) {
 			continue
 		}
 		chatsDir := filepath.Join(tmpDir, hd.Name(), "chats")