RULES.md: DEBUG mode also enables debug logging and the screen name (closes #761)

The DEBUG Mode line now lists what a debug build does: the red banner
naming the current screen, debug-level logging, and the hardcoded test
recovery phrase. Wording as approved on the issue.

Model: opus-5-5

RULES.md

@@ -75,7 +75,8 @@ contradicts either, the originals govern.
 
 ## DEBUG Mode
 
-- [ ] DEBUG mode only enables: red banner + hardcoded test mnemonic
+- [ ] DEBUG mode only enables: red banner naming the current screen, debug-level
+      logging, and the hardcoded test recovery phrase
 - [ ] No `if (DEBUG)` branches that skip functionality or bypass security
 - [ ] New DEBUG conditionals require explicit project owner approval