feat(ui,ui-server)!: remove Suspense — loading UX is early-return + query.loading [#2985]

[viniciusdacal]

Summary

Closes #2985.

• Suspense is rejected as a Vertz primitive. Vertz's signal/reactivity model already handles loading states via query().loading plus compiler-supported early-return guards (if (q.loading) return <Loading/>; return <Real/>) — which also keeps q.data typed-defined past the guard so APIs like form(..., { initial: () => q.data }) work without null checks.
• The Suspense we shipped was half-wired. The Suspense component existed in @vertz/ui but had no JSX-compatible children contract (children: () => JsxElement vs how the compiler wraps children). It was never used as JSX anywhere in the repo and never documented in mint-docs. The parallel __suspense VNode streaming protocol in @vertz/ui-server (SuspenseVNode, createSlotPlaceholder, createTemplateChunk) was dead code — nothing in shipped code produced __suspense nodes. Both are gone.
• Loading docs updated. New "Early return when you need loaded data" section in mint-docs/guides/ui/data-fetching.mdx documenting the replacement pattern with a form-on-loaded-data example and the flat-guard constraint.

Public API Changes

Breaking removals from @vertz/ui:

• Suspense component
• SuspenseProps type

Breaking removals from @vertz/ui-server:

• createSlotPlaceholder
• resetSlotCounter
• createTemplateChunk
• RenderToStreamOptions (and the nonce option on renderToStream)
• renderToStream(tree, options?) is now renderToStream(tree) — fully synchronous, single HTML chunk.

Internal cleanup:

• error-boundary-context.ts (the pushErrorHandler/popErrorHandler/getCurrentErrorHandler stack used only by Suspense) removed. ErrorBoundary keeps its synchronous try/catch + retry unchanged.

Commits

• 057b1607a — main removal
• 8528eee17 — adversarial-review follow-up: drop stale nonce Options block + CSP Nonce Support section from @vertz/ui-server README
• 87329972a — oxfmt fix

Adversarial Review

• Review written to reviews/remove-suspense/phase-01-removal.md — one BLOCKER found (stale README docs), fixed in 8528eee17.

Test plan

• vtz test on @vertz/ui — 2461 passed
• vtz test on @vertz/ui-server — 1270 passed / 60 skipped / 15 todo
• tsgo --noEmit on both packages — clean
• oxlint — 0 errors
• oxfmt --check — clean
• cargo test --all — 47 passed
• cargo clippy --all-targets -- -D warnings — clean
• cargo fmt --all -- --check — clean
• Full bun run ci:build-typecheck:affected — 40/40 pass
• Repo-wide grep: no remaining Suspense/__suspense/SuspenseVNode/SuspenseProps/createSlotPlaceholder/resetSlotCounter/createTemplateChunk/slot-placeholder/template-chunk/error-boundary-context/RenderToStreamOptions references outside CHANGELOGs, plans/, and the changeset file itself.

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