Lsp Navigation

LSP navigation

1. lsp_diagnostics beats a full build for "did my edit compile". After editing a file, one diagnostics call answers it in milliseconds. A full cargo check or tsc run is for the end of a task, not every edit.
2. lsp_references finds real usages. Text search finds the name in comments, strings, and unrelated scopes; references finds call sites. Use it before renaming or deleting anything. It takes a file plus a position, so search for the symbol first, then pass the position of one hit.
3. lsp_definitions jumps to the source. Use it when a call site's types are unclear and you need the signature, instead of guessing the file path and reading it.
4. Line and character are zero-based. The positions come from the file itself; if you just read the file, the line you saw is already the right number minus one.
5. The first call in a language is slow. The server starts and indexes on first use; rust-analyzer can take seconds on a large crate. That is startup cost, not a hang. Subsequent calls in the same session reuse the running server.
6. Missing servers are expected. If a tool says the language server is not installed, fall back to text search and a build; do not retry or tell the user to install anything unless they ask.