ask: serialize concurrent CLI with repo lock and stale PID recovery

Add advisory lock under .git/hexai-ask.lock around Taskwarrior execution,
with metadata (PID and process basename) and Linux /proc comm checks to
remove orphan lock files when the recorded holder is gone or not ask.

Extract internal/filelock for shared flock helpers; stats uses it too.

Made-with: Cursor

1 files changed, 0 insertions, 23 deletions

diff --git a/internal/stats/lock_posix.go b/internal/stats/lock_posix.go
deleted file mode 100644
index 2c41d31..0000000
--- a/internal/stats/lock_posix.go
+++ /dev/null
@@ -1,23 +0,0 @@
-//go:build !windows
-
-package stats
-
-import (
-	"errors"
-
-	"golang.org/x/sys/unix"
-)
-
-func tryLockFile(fd uintptr) error {
-	if err := unix.Flock(int(fd), unix.LOCK_EX|unix.LOCK_NB); err != nil {
-		if errors.Is(err, unix.EWOULDBLOCK) {
-			return errLockWouldBlock
-		}
-		return err
-	}
-	return nil
-}
-
-func unlockFile(fd uintptr) error {
-	return unix.Flock(int(fd), unix.LOCK_UN)
-}