fix(uninstall): include .diag files in diagnostic report cleanup matching

[PremPrakashCodes]

Summary

• Issue: [FEATURE] Add support for cleaning up diagnostic (.diag) files during uninstallation #747
• Added .diag to uninstall diagnostic report matching so cleanup discovery now includes .ips, .crash, .spin, and .diag files.
• Updated the regression test to verify .diag matching for the target app prefix and to prevent prefix-collision false positives.

Safety Review

• Does this change affect cleanup, uninstall, optimize, installer, remove, analyze delete, update, or install behavior?
  • Yes. It affects uninstall discovery behavior by expanding recognized diagnostic report extensions during app-related file lookup.
• Does this change affect path validation, protected directories, symlink handling, sudo boundaries, or release/install integrity?
  • No changes to path validation, protected directories, symlink handling, sudo boundaries, or release/install integrity.
• If yes, describe the new boundary or risk change clearly.
  • New boundary: uninstall diagnostic-report discovery now includes .diag files in addition to existing extensions. Risk change is low and scoped to matching logic only.

Tests

• List the automated tests you ran.
  • bats tests/uninstall.bats --filter "get_diagnostic_report_paths_for_app avoids executable prefix collisions"
  • bats tests/uninstall.bats --filter "find_app_files discovers user-level leftovers|get_diagnostic_report_paths_for_app avoids executable prefix collisions"
• List any manual checks for high-risk paths or destructive flows.
  • No additional manual destructive-flow checks were run for this patch.

Safety-related changes

• None.