Language server capability detection

The weaver-lsp-host crate initializes the LSP servers for Rust, Python, and TypeScript and records which core requests each server advertises: textDocument/definition, textDocument/references, diagnostics, and call hierarchy (textDocument/prepareCallHierarchy plus incoming/outgoing calls). These advertised capabilities are merged with any overrides provided via capability_overrides in weaver-config. force directives allow a request even when the server claims not to support it, while deny directives block the request regardless of the server report. When a request is rejected, the error explains whether the feature was disabled by configuration or simply absent from the server so operators and agents can adjust their plans without guesswork.

The daemon spawns real language server processes for each language and communicates via JSON-RPC 2.0 over stdio. The following binaries must be available in PATH:

When a language server binary is not found, the daemon returns a clear error message identifying the missing command. This allows operators to install the required tooling before retrying. Example:

failed to spawn rust language server: command 'rust-analyzer' not found

Language servers are initialized lazily when the first operation for that language is requested. The daemon sends the LSP initialize handshake followed by initialized, then routes subsequent requests through the established session.

Graceful shutdown is performed when the daemon stops: a shutdown request is sent to each running language server, followed by an exit notification. If a server does not exit within five seconds, it is terminated forcefully.