MCP: persistent port/token + mcp-remote shim recipe for Claude Code

Port (default 47821) and bearer token now persist to mcp.json with
OS-picked fallback if the port is taken; new Regenerate button in the
panel rotates the token and restarts the running server. rmcp's
DNS-rebinding host allowlist is disabled so WSL gateway IPs can
connect (bearer-auth handles the gatekeeping); the auth middleware
only enforces on /mcp paths so OAuth-discovery clients don't see a
Bearer challenge on /.well-known/* probes.

Claude Code's HTTP-MCP client currently tries OAuth and ignores
static `headers` auth (anthropics/claude-code#17152, #46879), so the
panel + README config snippet now uses `npx mcp-remote` as a stdio
shim that proxies the HTTP endpoint with the bearer baked in.

src/App.tsx

@@ -10,6 +10,7 @@ import {
   mcpStart,
   mcpStop,
   mcpStatus as mcpStatusCmd,
+  mcpRegenerateToken,
   mcpUpdateState,
   writeToPane,
   killPane,
@@ -343,6 +344,20 @@ export default function App() {
     }
   }, [notify]);
 
+  const regenerateMcpToken = useCallback(async () => {
+    try {
+      const st = await mcpRegenerateToken();
+      setMcpStatus(st);
+      notify(
+        st.running
+          ? "MCP token regenerated — update your client config"
+          : "MCP token regenerated",
+      );
+    } catch (e) {
+      notify(`MCP token regen failed: ${e}`);
+    }
+  }, [notify]);
+
   // On mount, sync our local mcpStatus with whatever's already running
   // (the backend persists state across HMR reloads).
   useEffect(() => {
@@ -1051,6 +1066,7 @@ export default function App() {
           status={mcpStatus}
           onStart={startMcp}
           onStop={stopMcp}
+          onRegenerateToken={regenerateMcpToken}
           onClose={() => setMcpPanelOpen(false)}
           allowedPaneCount={allowedPaneCount}
           totalPaneCount={leafCount(tree)}