Add printer status region primitive

• Status: Done
• Kind: Feature
• Authors: Jean Mertz git@jeanmertz.com
• Date: 2026-08-27
• Implements: 091

Adds the claim stack, Command variants, recv_timeout ticking, erase-before-write/redraw-after, the enabling predicate, row background, shutdown erasure, prompt-writer suspension, and the suspend_status guard to jp_printer. Regions are one row only (zero window budget), with unit tests against Printer::memory and an explicit terminal-capability override.