Accept initialize requests with out-of-range process IDs

The issue is in the workspace actor's decoding of InitializeParams. Look at the code that handles the initialize request, likely in a file related to the workspace actor or LSP initialization. The test a_process_id_that_cannot_be_represented_installs_no_monitor is a starting point but needs to be updated or a new workspace-level test added. Ensure the decode succeeds for out-of-range processId by either ignoring the field or handling it gracefully, while parent::process_id remains unchanged. Verify by running the new test and any existing LSP tests.

Context

Since #549, the workspace actor decodes initialize parameters as gen-lsp-types' InitializeParams, which types processId as Option<i32>. lsp-types 0.95 typed it as Option<u32>.

An editor that sends a processId above 2³¹−1 now has initialize rejected with InvalidParams (invalid value: integer '2147483648', expected i32), so the language server cannot start. The workspace does not use processId at all.

The protocol actor already handles this case on its own: parent::process_id reads processId from the raw JSON and declines to monitor an ID that does not fit in i32. The server test a_process_id_that_cannot_be_represented_installs_no_monitor expresses that intent, but it still passes because it uses a fake workspace and never exercises the real decoding.

LSP defines integer as a signed 32-bit value, so such IDs are outside the specification, and they are rare in practice. The server should still not refuse to start over a field the workspace ignores.

Goal

An out-of-range processId must not prevent initialize from succeeding. Parent process monitoring keeps its current behavior of skipping IDs it cannot represent.

Scope

• Decode only the initialize fields the workspace uses (capabilities and workspace folders), or otherwise stop an unrepresentable processId from failing the decode.
• Keep parent::process_id as the single owner of processId interpretation.

Tests

• A workspace-level test that sends initialize with processId: 2147483648 and receives an InitializeResult.
• Consider covering the same case end to end, since the existing server test cannot observe workspace decoding.