fix(store/posixage): always close file lock

[joe0BAB]

This is a very subtle leak of not closing the file lock correctly in certain circumstances.

At the beginning of the function, we have:

	var (
		err error
		fl  *os.File
	)

	defer func() {
		// we must always close the file on any error returned
		if err != nil && fl != nil {
			_ = fl.Close()
		}
	}()

This code relies on re-using the same err variable. And we missed that / created a new one that would shadow it on one code path.

[docker-agent]

Review Summary

Assessment: 🟢 APPROVE

The fix correctly addresses the variable shadowing issue described in the PR. By splitting the short variable declaration (:=) into a separate assignment (=) at line 92, the code now properly reuses the outer err variable. This allows the defer function to correctly close the file lock on error paths.

Analysis:

• ✅ The variable shadowing bug is fixed correctly
• ✅ The defer function will now trigger as intended when errors occur
• ✅ No new bugs introduced by the changes

Note: During review, a potential file handle leak was identified at line 89 (where a second openFile call could replace the first file handle without closing it). However, this issue exists in the unchanged surrounding code, not in the lines modified by this PR, so it's outside the scope of this review.