Two bugs reported after v2.2.0:
1. Input fields and textareas overflowed their container — typing in
Settings / SendModal / NewContactModal would push the border past
the card edge because the renderer's default box-sizing was
content-box and `width: 100%` + padding pushed widths past parents.
Added `*, *::before, *::after { box-sizing: border-box; }` to
index.html. Removes the need for per-element `boxSizing: 'border-box'`
(the existing sprinkles stay for clarity but are now redundant).
2. App went blank when opening a chat — any throw inside Conversation
propagated up through Shell and wiped the whole window, with no way
to navigate out. Added PaneBoundary, a React error boundary scoped
to one Shell pane, keyed on `${section}-(list|detail)` so it resets
when the user switches section. Now a crash shows an inline error
card with message + stack + Retry, while NavBar + StatusBar stay
usable.
Also hardened Conversation against edge cases that were candidates
for the original crash:
* `name` always falls back to shortAddr(address) if all other
branches produce an empty string.
* first letter used for the avatar is computed once, guarded
against empty input with a `?` fallback.
* Header name + short-address line get whiteSpace/overflow/ellipsis
so very long contacts no longer escape the 32px wide sub-column
the way they did for the reporter.
Fonts normalised in the global CSS too — inputs/textareas/buttons now
inherit `font-family` instead of the browser default, which was
breaking the visual rhythm in the Settings cards.
