[E1] Chord inspector: author chord name + per-string fingering

[byrongamatos]

Author chord name + per-string fingering (+ displayName, template arp) on the stable model from #3.

Work

• Inspector UI: name field + per-string finger picker (0=open, 1–4) + arp toggle. Reuse existing technique-toggle/prompt patterns.
• Add backend emission for displayName + template arp in routes.py (sloppak wire + XML) so they round-trip (E0 deferred these).

Depends on #3. Part of got-feedBack/feedBack#334.