fix(systematic-debugging): defuse Claude Code ultrathink keyword scanner trigger (#1558)

The "Signals You're Doing It Wrong" bullet in systematic-debugging/SKILL.md
contains the literal token Claude Code's runtime scans for in tool result
bodies. Every Skill-tool invocation of this skill caused the harness to
inject a spurious system-reminder claiming the user requested deeper
reasoning, silently bumping every session into extended thinking.

Replace the bullet's spelling so the contiguous letter sequence the scanner
matches is broken with a hyphen. The signal text remains recognizable to
the agent and the documented action ("Question fundamentals, not just
symptoms") is unchanged.

Fixes obra/superpowers#1283

skills/systematic-debugging/SKILL.md

@@ -237,7 +237,7 @@ If you catch yourself thinking:
 - "Is that not happening?" - You assumed without verifying
 - "Will it show us...?" - You should have added evidence gathering
 - "Stop guessing" - You're proposing fixes without understanding
-- "Ultrathink this" - Question fundamentals, not just symptoms
+- "Ultra-think this" - Question fundamentals, not just symptoms
 - "We're stuck?" (frustrated) - Your approach isn't working
 
 **When you see these:** STOP. Return to Phase 1.