Allow deleting individual entries from recent generations history

[naheel0]

Summary

The recent-generations history panel (added in #162 / PR #224) only supports clearing the entire history. Users cannot remove a single outdated or unwanted generation entry without deleting everything.

Background

A removeHistoryEntry helper already exists at src/lib/generationHistory.ts:109 but is dead code — it is only referenced in unit tests, never used by the UI.

Proposed scope

• Add a per-entry delete control (e.g. an X / trash icon on hover) to each row in GenerationHistory.tsx.
• When an entry is deleted:
  • Remove it from persisted local history (removeHistoryEntry).
  • Remove it from in-memory state in GeneratePageClient.tsx.
  • If the deleted entry was the active one, clear activeHistoryEntryId.
• Keep the existing "Clear history" option as-is.

Acceptance criteria

• Users can delete any single history entry without affecting the others.
• Deleting the currently active entry unhighlights it and clears the active id.
• Deleted entries are not restored after a page refresh (persisted removal).
• Copy/download controls and sanitization are unaffected (no changes outside the history panel).

[anshk1234]

hey
can i work on this ??