Mockup: in-editor field protection toggle

[RisingOrange]

Design mockup for moving the "protect fields" UI out of its separate browser-context-menu dialog and into the note editor itself, so users can see each field's protection state at a glance and toggle it in place.

This is intentionally unpolished — it's being put up as a draft so the team can pull the branch, open a note in the editor, take screenshots of variants, and decide on the final direction before we invest in productionizing it.

Related issues

• Closes #

Proposed changes

• New module ankihub/gui/field_protection.py injecting a small padlock button into each field header in the note editor.
• Unprotected fields show a faint outline padlock; protected fields show a filled amber padlock and get a 3px amber inset left border on the field body for at-a-glance visibility.
• Clicking a padlock toggles the AnkiHub_Protect::<FieldName> tag on the note, persists via col.update_note, and reloads the editor so the UI reflects the new state.
• AnkiHub_Protect::All is handled: toggling one field off expands it into per-field tags minus the unprotected one; toggling the last missing field back on collapses to ::All.
• Gated on ankihub_db.is_ankihub_note_type(...) and skips the internal ankihub_id field.
• Existing browser-context-menu "Protect fields" dialog is untouched — still the right UI for bulk operations across multi-selected notes.

Only per-note (tag-based) protection is surfaced. Per-notetype protection (ProtectedFieldsSet) is a deliberate follow-up, possibly as a second icon or a dropdown on the same control.

How to reproduce

1. Check out this branch and install/reload the addon in Anki.
2. Open any note that belongs to an AnkiHub-synced deck (browser → double-click a note, or Add Cards on an AnkiHub note type).
3. Each field header now has a small padlock to the left of the <> HTML toggle area.
4. Click a padlock to flip its state — the body picks up an amber left border and the tag is written/removed on the note.

Screenshots and videos

To be added once we pick a variant.

Further comments

Open design questions for team input:

• Icon placement. Currently the padlock lands in the field's label/header container (near the field name). An alternative is putting it immediately left of the <> toggle to group per-field controls together. Trade-off: state indicator vs. action cluster. Easy to flip either way.
• Color. Amber (#f59e0b) for "protected". Neutral choice — red reads as danger/error, green reads as "good", blue reads as "info/link". Happy to try alternatives.
• Body tint. Field body gets a 3px inset amber left shadow when protected. Could also be a background tint, border, or removed entirely if we want the header icon to carry all the visual weight.
• Anki-version robustness. Header DOM injection uses pickHeader() with fallbacks (.label-container, .field-state, [class*="label"], firstChild). Works on Anki 25.09.2. Older versions may place the icon unexpectedly — needs hardening before ship.