ui: edit/delete buttons for custom files

- each row now shows Edit and Delete buttons (same styling as the
  profiler list buttons) instead of the red X glyph
- Edit reloads the entry into the top form: the Add button becomes
  Save (data-l10n updated too) and a Cancel button appears; submit
  updates the entry in place, recomputing fid/parentFid and excluding
  the edited row from the duplicate-path check
- Delete removes without confirmation; deleting the row being edited
  cancels the edit and an earlier deletion shifts the edit index
- pysimCustomAdd renamed to pysimCustomSubmit; tests for the whole
  flow; SW cache v114 -> v115.

README.md

@@ -538,7 +538,8 @@ Files not in pysim's model can be added manually:
 1. Switch to the **Custom files** tab in the Profiler list
 2. Enter the file path (e.g., `3F00/6F46`) and an alias (e.g., `EF.SPN`)
 3. Click **Add** — the file appears in the tree in italics (unverified)
-4. Click the file to verify existence — on success, it behaves like a model file
+4. Use **Edit** on a row to reload it into the form (the button becomes **Save** and a **Cancel** button appears) or **Delete** to remove it
+5. Click the file to verify existence — on success, it behaves like a model file
 
 Custom files persist in `localStorage` across sessions. Export/import as JSON for sharing.