0.3.1

Release v0.3.1 — join any realm context when adding a widget (UI v78)

Re-applies the add/edit context work on top of v0.3.0; it was written
against 4331358 and main moved on, so it never reached the mainline.

The context list only offered contexts that already held a compatible
provider or consumer, so installing new equipment into an existing
space — "room 123", nothing compatible in it yet — left minting a
duplicate context as the only route, and the realm ended up carrying two
contexts of the same name with nothing binding.

The dialog now also lists every OTHER realm context, in a disclosure
that opens by itself when nothing compatible exists (exactly the case
where the old copy sent people to New context). One search box filters
current, compatible and other contexts together, matching on display
name, any other observed name for that context, and the id — so typing
"123" finds Room 123 however the realm spells it.

Filtering toggles [hidden] on existing rows instead of re-rendering, so
the search never loses focus and no checked box is dropped; a checked
row stays visible even when the query excludes it, and the "nothing
matched" note counts query hits rather than visible rows. Live keys
pushes repaint the matching and other groups independently, each
carrying its checked ids across, then re-apply the active query.

UI stamp goes to v78 — v77 was already taken by v0.3.0. test-ui.js gains
15 checks; retract, spec, faceplate and library suites all still pass.
Bumps package version + lockfile and repins INSTALL.md at v0.3.1.

Claude-Session: https://claude.ai/code/session_01GonRXxFHsZdobbv8Y2zvHC