feat(pvm): mediate UI platform output

[replghost]

Summary

DotLi's PolkaVM sandbox consumes PVM Host Runtime v0.1.10 UI output v1.

• validate structured cursor, mutable-text, IME geometry, clipboard-text, and URL output at the sandbox boundary
• apply cursor and IME-agent state inside the app frame
• focus and position the hidden text agent from guest IME geometry
• preserve the full 4× surface-density range
• send one sensitive command to the owning Host per output
• arm that channel only from trusted keyboard or pointer input
• validate app origin, iframe source, activation identity/expiry, command shape, byte bounds, and HTTP(S) scheme again in the Host
• consume the activation before executing one clipboard or navigation request
• keep clipboard permission off the cross-origin app iframe
• pin the source-built runtime and browser assets through host-rust-core#599 / PVM Host Runtime v0.1.10

This pull request is stacked on #185, which introduces the PolkaVM browser path.

Verification

• sandbox PVM tests: 27 passed
• host bridge tests: 28 passed, including origin/source/activation/one-command policy
• sandbox and UI typechecks pass
• sandbox and UI ESLint pass
• source-built runtime assets match the immutable bridge pin
• production host/sandbox build passes
• a real App Kit egui-starter CAR ran on the compiler backend with valid Tri2D output
• browser interaction produced cursor=text, focused/positioned the IME textarea, and emitted a Host message containing only CopyText("Hello from PolkaVM")
• Chromium confirmed transient user activation remains active in the Host for both the activation and command messages

[github-actions]

⚡ Performance Report

⚠️ No baseline found on main. This PR's results are recorded but cannot be compared.
Merge to main to establish a baseline.

[github-actions]

Bundle Size Report

Chunks over 500 KB:

File	Raw	Brotli	Gzip
host/assets/paseo.smol-DboPaEh1.json	1.84 MB	941.7 KB	1019.4 KB
host/assets/paseo-people-next.smol.json	3.36 MB	1.68 MB	1.82 MB
host/assets/smoldot.js	3.05 MB	2.27 MB (-17 B)	2.28 MB
host/assets/smoldot_worker.js	3.02 MB	2.26 MB	2.27 MB
host/assets/truapi_server_bg.wasm	7.20 MB	5.29 MB	5.56 MB
host/assets/wasm/web/truapi_server_bg.wasm	7.20 MB	5.29 MB	5.56 MB
sandbox/pvm-runtime/pvm-browser-runtime.wasm	1006.6 KB	167.6 KB	226.5 KB
Total	28.02 MB (+1.21 MB)	18.29 MB (+238.2 KB) (-35%)	19.19 MB (+303.8 KB)

All files

File	Raw	Brotli	Gzip
host/.well-known/apple-app-site-association	505 B	505 B	505 B
host/.well-known/assetlinks.json	2.1 KB	343 B	427 B
host/assets/bridge.js	74.0 KB (+3.5 KB)	20.3 KB (+1000 B)	23.3 KB (+1.1 KB)
host/assets/browser.js	22.9 KB	7.6 KB (+13 B)	8.6 KB (-1 B)
host/assets/client.js	100.1 KB	29.4 KB (+20 B)	32.4 KB (+3 B)
host/assets/dist.js	39.0 KB (+6 B)	12.8 KB (-37 B)	14.5 KB (+40 B)
host/assets/dotli-debug-bus.js	710 B	710 B	710 B
host/assets/get-sync-provider.js	2.8 KB	1.1 KB (-2 B)	1.2 KB (-3 B)
host/assets/hex.js	154 B	154 B	154 B
host/assets/index.js	234.6 KB (+6.2 KB)	58.8 KB (+1.6 KB)	70.3 KB (+2.0 KB)
host/assets/index.css	55.1 KB	8.6 KB	9.8 KB
host/assets/manifest.js	19.6 KB (-3.0 KB)	6.5 KB (-740 B)	7.2 KB (-818 B)
host/assets/panel.js	76.4 KB (+128 B)	20.6 KB (+41 B)	23.2 KB (+2 B)
host/assets/paseo.smol-DboPaEh1.json	1.84 MB	941.7 KB	1019.4 KB
host/assets/paseo-people-next.smol.json	3.36 MB	1.68 MB	1.82 MB
host/assets/paseo.smol.json	25.2 KB	5.6 KB	6.7 KB
host/assets/previewnet.smol.json	63.7 KB	7.6 KB	13.1 KB
host/assets/resolve.js	156 B	156 B	156 B
host/assets/rpc-resolve.js	2.5 KB	1.0 KB (-4 B)	1.2 KB
host/assets/smoldot.js	3.05 MB	2.27 MB (-17 B)	2.28 MB
host/assets/smoldot_worker.js	3.02 MB	2.26 MB	2.27 MB
host/assets/spans.js	2.6 KB	1.1 KB	1.3 KB
host/assets/src.js	1.8 KB	848 B (+4 B)	946 B (+1 B)
host/assets/styles.css	15.3 KB	3.3 KB	3.8 KB
host/assets/truapi_server_bg.wasm	7.20 MB	5.29 MB	5.56 MB
host/assets/wasm/web/README.md	13.4 KB	13.4 KB	13.4 KB
host/assets/wasm/web/package.json	371 B	371 B	371 B
host/assets/wasm/web/truapi_server.d.ts	12.6 KB	12.6 KB	12.6 KB
host/assets/wasm/web/truapi_server.js	49.7 KB	7.9 KB	9.2 KB
host/assets/wasm/web/truapi_server_bg.wasm	7.20 MB	5.29 MB	5.56 MB
host/assets/wasm/web/truapi_server_bg.wasm.d.ts	4.0 KB	4.0 KB	4.0 KB
host/assets/web.js	18.2 KB (+6 B)	4.6 KB (-7 B)	5.1 KB (-4 B)
host/assets/worker-runtime.js	28.9 KB (+28.8 KB)	6.8 KB (+6.7 KB)	7.7 KB (+7.6 KB)
host/assets/worker-runtime.js	106 B	106 B	106 B
host/assets/ws.js	23.1 KB	7.5 KB (+5 B)	8.2 KB (-3 B)
host/dotli.png	11.5 KB	11.5 KB	11.5 KB
host/favicon.svg	1.8 KB	1.8 KB	1.8 KB
host/host-sw.js	2.7 KB	1.1 KB (-3 B)	1.3 KB (-5 B)
host/icon-192.png	12.5 KB	12.5 KB	12.5 KB
host/icon-512.png	42.8 KB	42.8 KB	42.8 KB
host/index.html	29.1 KB	5.4 KB (+3 B)	6.7 KB
host/manifest.webmanifest	441 B	441 B	441 B
host/workbox.js	14.8 KB	4.6 KB	5.1 KB
sandbox/app-sw.js	9.7 KB (+52 B)	3.2 KB (+22 B)	3.6 KB (+18 B)
sandbox/assets/bitswap-bridge.js	840 B	840 B	840 B
sandbox/assets/fetch.js	3.4 KB	1.2 KB (+1 B)	1.4 KB (+3 B)
sandbox/assets/index.js	162.7 KB (+42.3 KB)	46.3 KB (+12.0 KB)	54.2 KB (+13.8 KB)
sandbox/assets/index.css	55.1 KB	8.6 KB	9.8 KB
sandbox/favicon.svg	1.8 KB	1.8 KB	1.8 KB
sandbox/index.html	1.7 KB	582 B (+2 B)	784 B (-2 B)
sandbox/pvm-runtime/LICENSE-MPL-2.0	16.3 KB	16.3 KB	16.3 KB
sandbox/pvm-runtime/PolkaVM-LICENSE-APACHE	10.6 KB	10.6 KB	10.6 KB
sandbox/pvm-runtime/PolkaVM-LICENSE-MIT	1023 B	1023 B	1023 B
sandbox/pvm-runtime/SOURCE	389 B	389 B	389 B
sandbox/pvm-runtime/pvm-browser-runtime.wasm	1006.6 KB	167.6 KB	226.5 KB
sandbox/pvm-runtime/pvm-gpu-worker.js	55.6 KB	9.8 KB	11.2 KB
sandbox/pvm-runtime/pvm-wasm-worker.js	73.8 KB	11.9 KB	14.0 KB
Total	28.02 MB (+1.21 MB)	18.29 MB (+238.2 KB) (-35%)	19.19 MB (+303.8 KB)

_{Commit: 7ce1f83}

[github-actions]

⚠️ E2E Product suite skipped — Nova signing bot is unavailable.

This is a Nova-side outage and not a dot.li test failure. Re-run
from the Actions tab once the bot recovers.

Logs: https://github.com/paritytech/dotli-community/actions/runs/33824435869