fix(ci): move tracker markers above tables, use line offsets

HTML comments between table rows broke markdown rendering. Moved both
tracker markers above table headers, updated workflow to use offsets:
- QUICK-REF-MAX: data row at marker + 3
- VERSION-INSERT: insert at marker + 2

Co-Authored-By: Claude <noreply@anthropic.com>

COMPATIBILITY.md

@@ -4,9 +4,9 @@ This document tracks the compatibility between **Gitea Mail Templates** releases
 
 ## Quick Reference
 
+<!-- TRACKER:QUICK-REF-MAX -->
 | Template Release | Min Gitea | Max Tested Gitea | Status |
 |-----------------|-----------|-----------------|--------|
-<!-- TRACKER:QUICK-REF-MAX -->
 | **v1.0.x**      | **1.25.0** | **1.26.4** | ✅ Active |
 
 > **Latest verified:** All 11 templates pass validation against Gitea 1.26.4 data contexts. <!-- TRACKER:LATEST-VERIFIED -->
@@ -21,9 +21,9 @@ gitea --version
 
 ## Gitea Version History — Mail Template Impact
 
+<!-- TRACKER:VERSION-INSERT -->
 | Gitea | Release Date | Mail Template Changes | Breaking? |
 |-------|-------------|----------------------|-----------|
-<!-- TRACKER:VERSION-INSERT -->
 | **1.26.4** | 2026-06-21 | None — hotfix release | No |
 | **1.26.3** | 2026-06-20 | None — security release | No |
 | **1.26.2** | 2026-05-20 | None — security + bug fixes | No |