Add build artifacts and scratch files to .gitignore

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -16,3 +16,15 @@ sx-rust/
 shared/static/scripts/sx-full-test.js
 hosts/ocaml/_build/
 hosts/ocaml/browser/sx_browser.bc.wasm.assets/
+hosts/ocaml/browser/sx_browser.bc.wasm.assets.bak/
+hosts/ocaml/bin/mcp_tree_built.exe
+hosts/ocaml/hosts/
+hosts/ocaml/test-results/
+shared/static/wasm/sx_browser.bc.wasm.assets/
+.claude/worktrees/
+tests/playwright/test-results/
+test-case-define.sx
+test-case-define.txt
+test_all.js
+test_final.js
+test_interactive.js