feat(crg): add Current Grade badge anchor to READINESS.md

Adds **Current Grade:** D line before the Grade Reference section,
providing a machine-readable anchor for CRG badge tooling.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: hyperpolymath

docs/READINESS.md

@@ -6,6 +6,8 @@
 **Assessed:** 2026-03-09
 **Assessor:** Jonathan D.A. Jewell
 
+**Current Grade:** D
+
 ## Grade Reference
 
 | Grade | Name                  | Release Stage      | Meaning                                              |