fix(badges): cancel edit state on field switch, not just on explicit cancel

toggle_field only changed active_field — it never called cancel_field for the
previously open field. Unsaved typed values stayed in edit_full_name_override etc.,
so reopening a field would show the stale typed value and re-apply it to the badge
preview, even though the user had already moved on.

New logic: capture was_open, always call cancel_field for the current field (resets
edit vars + sets active_field = null), then open the new field if it wasn't the one
being closed. Closing a field by re-clicking its pencil now also discards unsaved state,
consistent with the explicit [X] button behavior.

Also: add global placeholder CSS fix to TODO__Agents.md (scoped workaround already
in ae_comp__badge_print_controls; long-term fix belongs in app.css or theme file).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

documentation/TODO__Agents.md

@@ -145,6 +145,26 @@ functionality, but pollutes the console and may cause unhandled promise rejectio
 - **Badge print controls UX polish:** Scott has improvements in mind — TBD next session.
   File: `ae_comp__badge_print_controls.svelte`.
 
+### [CSS] Global placeholder text color — too dark in light mode
+Placeholder text inherits full input text color in light mode (Tailwind CSS default), making
+placeholders indistinguishable from filled-in values. Most visible in badge print controls
+where placeholders show the actual badge value (e.g. "John Smith").
+
+Workaround: scoped `::placeholder` rule added to `ae_comp__badge_print_controls.svelte`
+(gray-400 light / gray-500 dark) — `commit 7733ef8`.
+
+**Long-term fix:** Add a global rule to the main CSS (e.g. `src/app.css` or a theme file):
+```css
+::placeholder {
+    color: #9ca3af; /* gray-400 */
+    opacity: 1;     /* overrides Firefox's 0.54 default */
+}
+.dark ::placeholder {
+    color: #6b7280; /* gray-500 */
+}
+```
+Once the global rule is in place, remove the scoped workaround from the badge controls.
+
 
 
 ### [Leads] Exhibitor Lead Scanning — IN PROGRESS (demo-ready prep)