feat(ext): add GLYPH_NEXT and replace ASCII arrows with ▸

Replaces the ASCII rightwards arrow → with U+25B8 ▸ in settings-vault
buttons. Matches the existing ▾/▸ disclosure-glyph family.

extension/src/shared/glyphs.ts

@@ -16,6 +16,7 @@ export const GLYPH_TRASH         = '▦';   // sidebar trash nav
 export const GLYPH_DEVICES       = '⌬';   // sidebar devices nav
 export const GLYPH_SETTINGS      = '⚙';   // sidebar settings nav
 export const GLYPH_LOCK          = '⏻';   // sidebar lock nav
+export const GLYPH_NEXT          = '▸';   // forward / next button (matches ▾/▸ disclosure family)
 
 /// Inline HTML snippet for the required-field pill. Use after a label's text:
 ///   `<label class="label" for="f-title">title ${REQUIRED_PILL_HTML}</label>`