feat(mini-lynx): close the production gaps — errors, event transport, global props

[amritk]

Three things stood between a green suite and an app shipping this, and they
share a shape: each is a place where the runtime is the outermost JavaScript
frame, with native code or the job queue above it and no caller to hand a
problem to.

• setErrorHandler, and guards at every boundary the engine calls in on. A
  handler throwing inside the engine's dispatch and a commit throwing on the
  promise job queue were both undefined behaviour with nothing listening.
  Errors are now caught, tagged with their source, and reported; handlers on
  one (type, name) are isolated from each other, a failed commit no longer
  wedges the scheduler, and /recycle answers the engine's own -1 rather than
  unwinding into list layout mid-scroll.
• setEventTransport plus /bridge. The worklet round trip is the one engine
  assumption here that hardware could still disprove, and the failure would be
  silent and total. The listener form is now a seam with the worklet transport
  as its default, and the string-handler fallback ships with the app owning the
  wire back from the background thread.
• globalProps(). The engine calls exactly one updateGlobalProps, so an app
  cannot own that slot and still let a component react to a change. renderPage
  claims it and turns it into a signal.

renderPage also emits firstScreen when the root component throws: it is the
platform's cue to stop waiting, not a report of success.

Core budget moves 5064 -> 5414 gzipped to cover all of it.

Co-Authored-By: Claude Opus 5 [email protected]

📦 Bundle-size delta vs main (55e928b → dd123bc)

Package	Entry	main	PR	Δ
mini	core (.)	3,156 B	3,156 B	+0 B (+0.0%) ⚪
mini	flow	4,083 B	4,083 B	+0 B (+0.0%) ⚪
mini	router	4,158 B	4,158 B	+0 B (+0.0%) ⚪
mini	forms	4,259 B	4,259 B	+0 B (+0.0%) ⚪
mini	query	1,988 B	1,988 B	+0 B (+0.0%) ⚪
mini-lynx	core (.)	5,459 B	5,459 B	+0 B (+0.0%) ⚪
mini-lynx	flow	4,850 B	4,850 B	+0 B (+0.0%) ⚪
mini-lynx	router	5,856 B	5,856 B	+0 B (+0.0%) ⚪
mini-lynx	forms	5,272 B	5,272 B	+0 B (+0.0%) ⚪
mini-lynx	query	1,990 B	1,990 B	+0 B (+0.0%) ⚪
mini-lynx	testing	2,451 B	2,451 B	+0 B (+0.0%) ⚪

_{Gzipped bytes of each bundled entry (esbuild, minified, browser/es2022, optional peer deps external). Bundling is deterministic, so unlike a timed benchmark these numbers carry no noise and every Δ is exact. ⚪ within ±0.5% · 🟢 smaller · 🔴 larger. Each package's core (.) must stay flat as subpath features land — that is the whole charter, and src/core-size-budget.test.ts holds the absolute ceiling.}