fix: diagram routing bug + unified icon system
Fix diagram documents opening as spreadsheets in the All Documents list
by replacing hardcoded 2-type ternary with docPath()/docIcon() helpers.
Also fix buildEditorUrl() to route all 5 document types correctly.
Replace all system emojis (U+1Fxxx) with consistent non-emoji unicode
symbols across all HTML and TS files. Deduplicate icons (diagram vs doc,
group vs ungroup, distribute H vs V). Create cards now match DOC_ICON_MAP.
Table toolbar arrows use safe arrow symbols.