docs(mcp-loader): add MCP-STREAMABLE-HTTP-CLIENT-SYNC token

RemoteMcpClient is vendored into mempalace-toolkit's mempalace.ts. Add a
sync token so mempalace-toolkit/scripts/check-mcp-client-sync.sh can detect
drift between this canonical copy and the vendored one. Comment-only.

extensions/mcp-loader.ts

@@ -306,6 +306,13 @@ class StdioMcpClient implements IMcpClient {
 
 // ── Streamable-HTTP MCP client (remote) ──────────────────────────────────────
 //
+// MCP-STREAMABLE-HTTP-CLIENT-SYNC: v1
+// Canonical copy. This class is VENDORED into
+// mempalace-toolkit/extensions/pi/mempalace.ts (adapted: pinned protocolVersion,
+// AbortController timeouts, alive/ensureAlive). When you change the
+// streamable-HTTP protocol handling here, bump the SYNC token in BOTH files.
+// mempalace-toolkit/scripts/check-mcp-client-sync.sh enforces the match.
+//
 // Per MCP spec 2025-03-26: a single endpoint URL accepts POST with a
 // JSON-RPC body. The server responds either with application/json (a
 // single response) or text/event-stream (an SSE stream containing the