chore: expand .gitignore for per-crate target dirs and local artifacts

* crates/*/target/ - per-crate build output (root /target/ was already
  covered, but workspace members' own target/ dirs were leaking through)
* .omo/ .sisyphus/ - local agent tooling state, not project content
* benchmark-report.md - output of cargo run -p log-viewer-bench,
  regenerated per run so should not be tracked

.gitignore

@@ -1,5 +1,13 @@
 /target/
+crates/*/target/
 *.swp
 *.swo
 .idea/
 .vscode/
+
+# Agent tooling state
+.omo/
+.sisyphus/
+
+# Benchmark output
+benchmark-report.md