Allow large remote app-server resume responses

[etraut-openai]

Why

Remote TUI resume uses the app-server websocket client. That client inherited tungstenite's default 16 MiB frame limit, so a large saved session could make thread/resume return a single JSON-RPC response frame that the client rejected before the TUI could deserialize or render it.

Fixes #19837

What Changed

• Configure the remote app-server websocket client with a bounded 128 MiB max frame/message size.
• Preserve the concrete remote worker exit reason when completing pending requests after a transport/read failure instead of replacing it with a generic channel-closed error.
• Add a regression test that sends a single >16 MiB JSON-RPC response frame and verifies the typed request succeeds.

Note: This isn't a perfect fix. It really just moves the limit to a much larger value. I looked at a bunch of other potential fixes (both server-side and client-side), and they all involved significant complexity, had backward-compatibility impact, or impacted performance of common use cases. This simple fix should address the vast majority of remote use cases.

Verification

I reproed the problem locally using a long rollout. Verified that fix addresses connection drop.