fix(m6-synthesis): inline [SUPERSEDED] tags and provenance tuples for all contradicting claims

Resolve 5 remaining M6 scrutiny round-3 BLOCKING documentation-precision issues:
- EVAL-COVERAGE.md ~line 10: inline [SUPERSEDED] prefix + historical past-tense rewrite
- ELEVATE-OR-KILL.md lines 79,85,99,100,107,108,118,124,128,171: inline [SUPERSEDED] tags on every ELEVATE/significance assertion
- ELEVATE-OR-KILL-SYNTHESIS.md lines 12,121,171: full provenance tuple (pre/post-edit + directional/significant/null + replicated/not) in same sentence

Banners are NOT sufficient — every individual contradicting line now carries inline marking.
All three scrutiny self-greps (a,b,c) clean; validate-skills.js + run-structural.js pass (exit 0).