fix: replace all remaining emoji with monochrome glyph constants

- trash.ts TYPE_ICONS map uses GLYPH_TYPE_* constants
- field-history.ts copy button uses GLYPH_COPY
- attachments-disclosure.ts thumbnail/icon uses GLYPH_TYPE_DOCUMENT
- settings.ts sync button uses GLYPH_SYNC
- document.ts thumb/sigblock/preview use GLYPH_TYPE_DOCUMENT + GLYPH_PREVIEW
- glyphs.ts adds GLYPH_COPY, GLYPH_SYNC, GLYPH_PREVIEW
- vault.ts adds GLYPH_DEVICES import + devices sidebar nav button

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

extension/src/shared/glyphs.ts

@@ -17,6 +17,9 @@ 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)
+export const GLYPH_COPY          = '⎘';   // copy to clipboard
+export const GLYPH_SYNC          = '⇅';   // sync / upload
+export const GLYPH_PREVIEW       = '⊕';   // preview / expand
 
 export const GLYPH_VAULT_TAB      = '⧉';   // U+29C9 pop-out to fullscreen vault tab