feat(lanes): add POST /:id/mcp/sync route (F1)

server/routes/lanes.js

@@ -34,6 +34,7 @@ const {
 const { withLaneLock } = require("../lib/lane-lock");
 const { checkSync, mergeSync, continueSync } = require("../lib/lane-sync");
 const { installAgents } = require("../lib/lane-agents");
+const { syncMcp } = require("../lib/lane-mcp");
 const { HOOKS, runHook, resolveProfile } = require("../lib/lane-profile");
 const { slotDirs } = require("../lib/lane-slots");
 const {
@@ -349,6 +350,27 @@ router.post("/:id/agents/install", sameOriginGuard, async (req, res) => {
   }
 });
 
+/**
+ * Give this lane the same MCP servers as its source repo — relocates the
+ * source repo's already-configured mcpServers (from ~/.claude.json) into
+ * <lane>/.mcp.json, pins Playwright's proof output dir, seeds Chromium
+ * profiles. Never automatic, same as proof-link/agents-install: a session
+ * calls this explicitly. Never touches permissions/settings.local.json —
+ * see the F1 design spec for why.
+ */
+router.post("/:id/mcp/sync", sameOriginGuard, async (req, res) => {
+  const lane = lanesLib.getLane(req.params.id);
+  if (!lane) return res.status(404).json({ error: { code: "ENOLANE", message: "lane not found" } });
+  try {
+    res.json(await syncMcp(lane));
+  } catch (err) {
+    if (err.code === "ENOMCPCONFIG") {
+      return res.status(400).json({ error: { code: err.code, message: err.message } });
+    }
+    res.status(500).json({ error: { code: err.code || "ERUNTIME", message: err.message } });
+  }
+});
+
 /**
  * A lane's working-copy facts: branch, short HEAD, that commit's subject, and
  * the uncommitted counts. Read-only, so no same-origin guard — that guard
@@ -593,6 +615,7 @@ function sendRuntimeError(res, err) {
     "EBADBRANCH",
     "EUNRESOLVED",
     "EMERGEUNCOMMITTED",
+    "ENOMCPCONFIG",
   ];
   if (badRequest.includes(err.code)) {
     return res.status(400).json({