Include first finding location in exit error output

[LarytheLord]

Summary

• add ParsePathsWithReport to expose summary metadata (files with findings + first finding location)
• keep existing ParsePaths behavior intact by delegating to the new report method
• include first finding: file:line:column in the --exit-1-on-failure error message
• add tests for parser report location and root command error formatting

Why

Closes #274 by making failure output immediately actionable even when users primarily see the terminal error line.

Validation

• Added/updated unit tests in pkg/parser/parser_test.go and cmd/root_test.go
• I could not run go test in this environment because the go binary is not installed.