Follow-Up to $43: Reorder Paste Stack entries by drag and drop

[alvst]

Dependency

This is a stacked follow-up to #33 and the underlying Paste Stack series (#29–#31). It should be reviewed and merged after that series. The feature commits are c39f06c and d803e44; prerequisite commits appear because upstream main does not yet contain Paste Stack.

What changed

• Adds drag handles and in-process drag-and-drop reordering for pending Paste Stack clips.
• Provides insertion targets between rows and at the end of the pending portion of the stack.
• Keeps pasted entries grouped after pending entries, preserving the next-to-paste workflow.
• Persists the reordered active stack.

Validation

• swift build
• git diff --check fork/focused/paste-stack-history-followup..HEAD
• Demo-mode UI verification of drag-and-drop reorder behavior.

Screenshot

Demo mode — Pesty window only.