feat(lsp): add SFTP remote runtime provider for LSP workspaces

Added sftpRemote.ts runtime provider that translates sftp:// URIs to

 file:// before sending to LSP servers, stripping host/credentials

 Register sftpRemoteRuntimeProvider in registerBuiltins.ts
Delegate transport to external-websocket provider since SFTP LSP
connections are handled via WebSocket tunnel

Author: gat0sy

src/cm/lsp/runtimes/registerBuiltins.ts

@@ -2,7 +2,10 @@ import { registerRuntimeProvider } from "../runtimeProviders";
 import builtinAlpineRuntimeProvider from "./builtinAlpine";
 import externalWebSocketRuntimeProvider from "./externalWebSocket";
 import webWorkerRuntimeProvider from "./webWorker";
+import { sftpRemoteRuntimeProvider } from "./sftpRemote";
 
 registerRuntimeProvider(builtinAlpineRuntimeProvider, { replace: true });
 registerRuntimeProvider(externalWebSocketRuntimeProvider, { replace: true });
 registerRuntimeProvider(webWorkerRuntimeProvider, { replace: true });
+registerRuntimeProvider(sftpRemoteRuntimeProvider, { replace: true });
+

src/cm/lsp/runtimes/sftpRemote.ts

@@ -0,0 +1,43 @@
+import type {
+    LspRuntimeProvider,
+    LspRuntimeContext,
+    LspRuntimeUriResolutionContext,
+    TransportDescriptor,
+} from "../types";
+import { getRuntimeProvider } from "../runtimeProviders";
+
+function sftpUriToFileUri(uri: string): string | null {
+    const match = /^sftp:\/\/[^/]*(\/.*)$/.exec(uri);
+    if (!match) return null;
+    const path = match[1].split("?")[0];
+    if (!path) return null;
+    return "file://" + path;
+}
+
+export const sftpRemoteRuntimeProvider: LspRuntimeProvider = {
+    id: "sftp-remote",
+    label: "SFTP Remote",
+    priority: -30,
+
+    canHandle(server, context) {
+        const uri = String(context.rootUri || context.uri || "");
+        return /^sftp:/i.test(uri);
+    },
+
+    resolveUris(server, context: LspRuntimeUriResolutionContext) {
+        const documentUri = sftpUriToFileUri(context.originalDocumentUri);
+        const rootUri = context.originalRootUri
+            ? sftpUriToFileUri(context.originalRootUri)
+            : null;
+        return { documentUri, rootUri, scope: "workspace" };
+    },
+
+    async start(server, context: LspRuntimeContext): Promise<TransportDescriptor> {
+        // Delegate transport to external-websocket provider
+        const external = getRuntimeProvider("external-websocket");
+        if (!external || !external.start) {
+            throw new Error("SFTP workspace requires external-websocket transport provider");
+        }
+        return external.start(server, context);
+    },
+};