chore: untrack Playwright MCP captures and root screenshot; trim docker build context

Also records the gitea runner durable fix in the launch checklist.

.gitignore

@@ -13,9 +13,11 @@ dist/
 npm-debug.log*
 .DS_Store
 
-# Test artifacts
+# Test artifacts and ad-hoc browser captures (Playwright MCP snapshots, root screenshots)
 test-results/
 playwright-report/
+.playwright-mcp/
+/*.png
 
 # Working/planning docs — kept on disk, not version-controlled (see docs/ for committed records)
 planning/