feat(context): promote MCP compactor to active locally

Add active-mode probe script and document mixed shadow/active promotion;
first active switch is MEMIND_MCP_COMPACT_MODE only.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/check-mcp-compact-active-local.mjs

@@ -0,0 +1,21 @@
+#!/usr/bin/env node
+/**
+ * Verify MCP compactor active promotion on this machine.
+ * Requires MEMIND_MCP_COMPACT_MODE=active in the environment (e.g. .env.local).
+ */
+import {
+  isMcpCompactActive,
+  resolveMcpCompactMode,
+} from '../mcp-result-compactor.mjs';
+
+const mode = resolveMcpCompactMode(process.env);
+console.log('MCP_COMPACT_ACTIVE_PROBE:');
+console.log(`  mode=${mode}`);
+console.log(`  active=${isMcpCompactActive(process.env)}`);
+
+if (mode !== 'active' || !isMcpCompactActive(process.env)) {
+  console.error('MCP_COMPACT_ACTIVE_FAIL: set MEMIND_MCP_COMPACT_MODE=active and restart Portal/MCP');
+  process.exit(1);
+}
+
+console.log('MCP_COMPACT_ACTIVE_OK');