Ignore audit reports, run logs, and per-crate target/ dirs

audit-out/ and audit-*.md are local report artifacts produced by the
PPCBUG audit pipeline; *.stdout/*.stderr/*.log are stress-harness run
captures. Switch /target/ to target/ so per-crate target dirs (e.g.
crates/xenia-app/target/ used as a stress-output sink) are also ignored.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1,4 +1,13 @@
-/target/
+target/
 *.iso
 *.xiso
 *.db
+
+# Audit reports / pre-pass findings (local artifacts, not source)
+audit-out/
+audit-*.md
+
+# Run logs from stress harnesses and ad-hoc captures
+*.stdout
+*.stderr
+*.log