chore(repo): move fork docs and logs under contrib/fractured-dev-extras

Stock AzerothCore does not ship CLAUDE.md, BUILD-NATIVE.md, or local build
logs at repo root. Park them under contrib/fractured-dev-extras/ so the
repo root stays close to upstream and dev clutter is contained.

- mv CLAUDE.md, BUILD-NATIVE.md -> contrib/fractured-dev-extras/
- mv build-worldserver.log + _build_paragon_*.log there (untracked / ignored)
- add contrib/fractured-dev-extras/README.txt explaining the layout
- gitignore: contrib/fractured-dev-extras/*.log

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitignore

@@ -123,3 +123,6 @@ local.properties
 
 # Local build artifacts (do not commit)
 build-worldserver.log
+
+# Local logs parked under contrib/fractured-dev-extras (see README there)
+contrib/fractured-dev-extras/*.log

contrib/fractured-dev-extras/README.txt

@@ -0,0 +1,13 @@
+Fractured / Paragon — non-runtime repo extras
+==============================================
+
+This folder holds material that is not required to configure, build, or run
+AzerothCore. Upstream AzerothCore does not ship these paths.
+
+Contents:
+- BUILD-NATIVE.md — fork-specific native build notes (moved from repo root).
+- CLAUDE.md — optional AI assistant context (moved from repo root).
+- *.log — local build logs (moved from repo root when present).
+
+Operational files (docker-compose.override.yml, env/dist, modules/mod-paragon,
+etc.) stay at their normal locations.