feat(lsp): add background daemon for language servers

README.md

@@ -40,9 +40,16 @@ npm install
 ## CLI Usage (for development/testing)
 
 ```
-tsx ./cli.ts <file> <lsp_command> <req_data_json>
+tsx ./cli.ts <file> <lsp_command> <req_data_json> [--no-daemon]
+tsx ./cli.ts daemon <status|stop>
 ```
 
+Requests use a long-lived background daemon by default. The daemon is
+autospawned on first use, keeps one language server alive per
+`(server.id, project root)`, and evicts idle servers after
+`ServerConfig.idleTtlMs` (default: 5 minutes). Pass `--no-daemon` to use the
+legacy one-shot path for debugging.
+
 `req_data_json` is the raw LSP params for the command, minus
 `textDocument.uri` (we inject that from `<file>`).
 
@@ -71,9 +78,15 @@ npm run lsp -- backend/api/server.go documentSymbol '{}'
 
 # Diagnostics
 npm run lsp -- backend/api/server.go diagnostics '{}'
+
+# Inspect/stop the background daemon
+npm run lsp -- daemon status
+npm run lsp -- daemon stop
 ```
 
-Set `LSP_DEBUG=1` to forward server stderr.
+Set `LSP_DEBUG=1` to forward server stderr to the daemon log. The daemon
+socket is `$XDG_RUNTIME_DIR/pi-lsp-$UID.sock` (tmpdir fallback); logs are in
+`/tmp/pi-lsp-daemon.log`.
 
 ## Adding A Server
 
@@ -97,7 +110,5 @@ Edit `server.ts`:
 
 ## Future
 
-- **Daemon with TTL** - `ServerConfig.idleTtlMs` is reserved for a future
-  daemon that keeps language servers alive per `(server.id, rootUri)` to
-  avoid cold-start latency. Not implemented; the CLI is short-lived and
-  spawns fresh each invocation.
+- **Daemon hardening** - persistent metrics, health checks, and richer status output.
+- **Build output** - ship compiled JS entrypoints instead of relying on tsx for development.