Skip non-string guid/updates entries in fragment merge

[tonythethompson]

Guard JSON reads for guid/updates so non-string values only skip the bad profile instead of skipping the whole fragment file.

Correct tracking

• GitHub: Skip non-string guid/updates entries in fragment merge tonythethompson/QuickShell#141
• PR: fix(fragment): guard guid/updates reads with JsonValueKind tonythethompson/QuickShell#135

Originally created on Trackdub team and synced to #8 by mistake. Moved to quickshell.

[linear-code]

TS-72

[tonythethompson]

Misrouted by Linear team/repo sync. This is QuickShell work, not Trackdub.

Correct tracking: tonythethompson/QuickShell#141
Shipped in: tonythethompson/QuickShell#135