fix(ai, web-ui): browser compatibility for pi-ai, update tsgo for decorator support

- Update @typescript/native-preview to 7.0.0-dev.20260120.1 (supports experimentalDecorators)
- Replace top-level node:fs, node:os, node:path imports with dynamic imports in stream.ts
- Replace top-level node:os import with dynamic import in openai-codex-responses.ts
- Replace top-level node:crypto, node:http imports with dynamic imports in openai-codex.ts
- Replace Buffer.from with atob for browser-compatible base64 decoding

fixes #873

package.json

@@ -29,7 +29,7 @@
 	"devDependencies": {
 		"@biomejs/biome": "2.3.5",
 		"@types/node": "^22.10.5",
-		"@typescript/native-preview": "7.0.0-dev.20251212.1",
+		"@typescript/native-preview": "7.0.0-dev.20260120.1",
 		"concurrently": "^9.2.1",
 		"husky": "^9.1.7",
 		"tsx": "^4.20.3",