AI codebase review

fix: duplicate search no longer hangs on files swapped for FIFOs

Candidates were reopened by path with os.Open after the scan. A file
replaced by a FIFO (or a symlink to one) blocked open(2) forever, and
context cancellation could not interrupt it, wedging the duplicate view
and --duplicates. Content is now opened with O_NOFOLLOW|O_NONBLOCK on
Unix; the existing regular-file check then skips it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/platform/open_other.go

@@ -0,0 +1,8 @@
+//go:build !unix
+
+package platform
+
+import "os"
+
+// OpenContent opens a file whose content is about to be read.
+func OpenContent(path string) (*os.File, error) { return os.Open(path) }

internal/platform/open_unix.go

@@ -0,0 +1,15 @@
+//go:build unix
+
+package platform
+
+import (
+	"os"
+	"syscall"
+)
+
+// OpenContent opens a file whose content is about to be read. It does not
+// follow a final symlink, and O_NONBLOCK keeps a FIFO swapped in since the
+// scan from blocking open(2) forever; callers still check the file type.
+func OpenContent(path string) (*os.File, error) {
+	return os.OpenFile(path, os.O_RDONLY|syscall.O_NOFOLLOW|syscall.O_NONBLOCK, 0)
+}