refactor(skills): drop social proof from systematic-debugging

Real-World Impact was statistics; the Overview opener restated the core
principle as motivation. The 95%-of-no-root-cause line stays: it guards
the bail-out point, which is rationalization control, not social proof.
Supporting Techniques/Related skills untouched (PR #1932 owns that).

Author: obra

skills/systematic-debugging/SKILL.md

@@ -7,8 +7,6 @@ description: Use when encountering any bug, test failure, or unexpected behavior
 
 ## Overview
 
-Random fixes waste time and create new bugs. Quick patches mask underlying issues.
-
 **Core principle:** ALWAYS find root cause before attempting fixes. Symptom fixes are failure.
 
 **Violating the letter of this process is violating the spirit of debugging.**
@@ -283,11 +281,3 @@ These techniques are part of systematic debugging and available in this director
 - **`root-cause-tracing.md`** - Trace bugs backward through call stack to find original trigger
 - **`defense-in-depth.md`** - Add validation at multiple layers after finding root cause
 - **`condition-based-waiting.md`** - Replace arbitrary timeouts with condition polling
-
-## Real-World Impact
-
-From debugging sessions:
-- Systematic approach: 15-30 minutes to fix
-- Random fixes approach: 2-3 hours of thrashing
-- First-time fix rate: 95% vs 40%
-- New bugs introduced: Near zero vs common