workspacePullState ignores a server's static workspaceDiagnostics capability

Description

workspacePullState() ignores a language server's static diagnostic capability, while its neighbour documentPullState() accounts for it. packages/opencode/src/lsp/client.ts:355-377:

function documentPullState() {
  ...
  supported: hasStaticPullDiagnostics || documentRegistrations.length > 0,
}

function workspacePullState() {
  ...
  supported: workspaceRegistrations.length > 0,
}

hasStaticPullDiagnostics (line 258) comes from the initialize response. diagnosticRegistrations is only populated by client/registerCapability (lines 180-189). Under LSP 3.17 a server may declare diagnosticProvider: { workspaceDiagnostics: true } statically and never dynamically register — in which case workspacePullState().supported is false and requestFullDiagnostics (line 429-440) never issues the workspace pull, returning no diagnostics with no error surfaced.

There's currently no way to fix it by just OR-ing the flag in: ServerCapabilities.diagnosticProvider is typed unknown (line 67) and only ever Boolean()-checked, so nothing can read workspaceDiagnostics off it. The type needs narrowing first, which is why I'm raising it rather than sending a patch.

I should be upfront: I found this by reading the code, not by hitting it with a real server — so it's possible the conservative behaviour is deliberate and you'd rather only trust dynamic registrations. If so, this is really a request for a comment saying that.

OpenCode version

1.18.14 (dev @ 24470e5)

Steps to reproduce

1. Use a language server that declares capabilities.diagnosticProvider = { workspaceDiagnostics: true, interFileDependencies: false } in its initialize response and never sends client/registerCapability for textDocument/diagnostic.
2. Run opencode debug lsp diagnostics <file> against a file that was never opened via textDocument/didOpen.
3. No diagnostics are returned; the workspace pull request is never sent.

Operating System

macOS 26.0.1