Add local Streams development support and stream browser improvements

[sorenbs]

Summary

• add local Streams development wiring and streams-only demo/runtime support
• add the stream event view improvements: search, follow modes, URL state, aggregation strip, diagnostics, and long-poll integration
• add a resizable Studio sidebar so long stream names can be revealed without changing layout code

Verification

• pnpm exec vitest run demo/ppg-dev/runtime-options.test.ts demo/ppg-dev/runtime.test.ts demo/ppg-dev/DemoShell.test.ts demo/ppg-dev/shutdown.test.ts ui/hooks/use-stream-details.test.tsx ui/hooks/use-stream-events.test.tsx ui/studio/views/stream/StreamView.test.tsx ui/studio/Navigation.test.tsx ui/studio/Studio.test.tsx
• pnpm exec vitest run ui/studio/context.test.tsx ui/studio/Navigation.test.tsx ui/studio/Studio.test.tsx
• pnpm typecheck
• Playwright validation on http://localhost:4310

[beseku]

One thing that maybe we can align on is the mechanic for streaming data like here and in Query insights. More relevant when we migrate the UI to align with Console, but it would be good to present the same way of pausing and resuming logs and log-adjacent data.