fix: bug fixes, test coverage, and CI workflow

- Fix Nodes.First() panic on empty slice (return nil)
- Fix ticker leak in archive.go (create once, defer Stop)
- Fix cookie path matching for empty and root paths
- Fix lost query params in google.go (u.Query().Set was discarded)
- Fix type assertion panic in useragents.go
- Fix dropped date parse error in powerball.go
- Remove unreachable dead code in megamillions.go and powerball.go
- Simplify document.go WaitForNetworkIdle, remove unused root field
- Remove debug fmt.Println calls across codebase
- Replace panic(err) with stderr+exit in all cmd/ programs
- Fix duckduckgo cmd: remove useless defer, return error on bad safesearch
- Fix archive cmd: ToConfig returns error instead of panicking
- Add 39+ unit tests across 6 new test files
- Add Gitea Actions CI workflow (build, test, vet in parallel)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/browser/main.go

@@ -74,6 +74,7 @@ func main() {
 	err := cmd.Run(context.Background(), os.Args)
 
 	if err != nil {
-		panic(err)
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
 	}
 }