fix(lsp): recover from handler panics and decode client uris

lsp/protocol.go

@@ -4,7 +4,7 @@
 // Package lsp implements a Language Server Protocol server for GAsm.  It
 // speaks JSON-RPC 2.0 over any io.Reader/io.Writer pair (normally standard
 // input/output) and provides completion, hover documentation, document
-// symbols, diagnostics and semantic-token highlighting — all backed by the
+// symbols, diagnostics and semantic-token highlighting, all backed by the
 // pure-Go lexer, parser, arch and lint packages.  It is the vendor-neutral
 // integration point: any LSP-capable editor can use it with no editor-specific
 // plugin code.
@@ -31,6 +31,7 @@ type rpcError struct {
 
 const (
 	errMethodNotFound = -32601
+	errInternalError  = -32603
 )
 
 // --- LSP positions and ranges ----------------------------------------------