feat(lsp): allow per-server diagnostics wait timeouts

[Yagi-Michael]

Issue for this PR

Closes #41218

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

DIAGNOSTICS_DOCUMENT_WAIT_TIMEOUT_MS (5s) and DIAGNOSTICS_FULL_WAIT_TIMEOUT_MS (10s) in lsp/client.ts are hardcoded. If a language server takes longer than that to produce diagnostics, the wait expires and the client returns nothing — which callers cannot distinguish from "the file is clean". That's the bug: silence and success look identical.

I hit this with clangd on an Unreal Engine project. One translation unit pulls in ~3,764 transitive headers and clangd needs about 20s to parse it, so the wait always expired and debug lsp diagnostics returned only the .clangd config file, never the file I asked about. It was not a misconfiguration — the same file compiles cleanly with clang++ -fsyntax-only using the flags from compile_commands.json, and a deliberately broken copy reports its error correctly.

This adds an optional per-server timeout: { document, full }, falling back to the existing constants when unset:

"lsp": {
  "clangd": {
    "command": ["clangd", "--compile-commands-dir=..."],
    "timeout": { "document": 60000, "full": 120000 }
  }
}

Why it works: create() in client.ts already receives input.server, and spawn() in lsp.ts already builds that object from the user's config, so the value just needs carrying through and reading at the six places the two constants are used.

One thing worth flagging for anyone adding LSP config fields later: the field has to be declared in both config/lsp.ts and v1/config/lsp.ts. A v1 config is decoded against v1's Entry before migrate.ts passes lsp through untouched, so a field present only in v2 gets silently stripped and never reaches the client. I patched only v2 first and the option appeared to do nothing.

Five files, +35/-6. I deliberately left DIAGNOSTICS_REQUEST_TIMEOUT_MS and INITIALIZE_TIMEOUT_MS alone — the latter is #23982 and belongs in its own change.

How did you verify your code works?

Ran the same command against the same file and the same clangd, changing only the config.

Before, and after with no timeout set (confirming defaults are unchanged):

$ opencode debug lsp diagnostics .../HGGameUserSettings.cpp
{
  "/work/ascent/UE/.clangd": []
}

~11s, requested file absent entirely.

After, with timeout configured, on a file containing a deliberate error:

zz_check.cpp: 2 diagnostics, 1 error
  Use of undeclared identifier 'this_symbol_does_not_exist'

~13s.

Also checked in a real session that the automatic post-edit path works: writing a broken .cpp now attaches Error [3:13] Use of undeclared identifier 'this_symbol_does_not_exist' to the write tool result, where before it attached nothing.

bun typecheck passes (30/30 packages) — the pre-push hook ran it.

Screenshots / recordings

Not a UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

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