[TASK] Improve confidence mapping in `subdomain_discovery` parser

[utksh1]

Summary

subdomain_discovery parser should expose more consistent confidence or evidence mapping for findings.

Why this task exists

Plugin quality depends on metadata clarity, parser stability, and predictable capability declarations. This task should tighten one plugin or plugin family without changing unrelated plugin behavior.

Scope

• Suggested files or directories: plugins/subdomain_discovery/parser.py
• Out of scope: broad multi-plugin refactors unless directly required to complete the target plugin change

Starting points

Review adjacent plugin metadata and parser tests in plugins/ and testing/backend/ to mirror established patterns.

Acceptance criteria

• The target plugin metadata or parser contract is improved as described
• Tests or fixtures are added when parser behavior changes
• Documentation stays in sync with the plugin contract if operator behavior changes

Test plan

Run the plugin-specific pytest file if one exists, or add focused parser coverage under testing/backend/ for the changed behavior.

Notes for contributors

Keep fixture data minimal and representative. Avoid opportunistic edits to unrelated plugin directories.

[mythri2405]

Hi @utksh1 ,

I would like to work on this issue under GSSoC'26. I have reviewed the requirements and am interested in implementing the proposed enhancement while following the project's contribution guidelines.

Could you please assign this issue to me?
I will start working on it and raise a PR soon after completing the implementation.

Thank you!

[tmdeveloper007]

This issue has been open for an extended period with no linked pull request and no recent activity. Suggesting closure to keep the issue tracker focused. Please feel free to reopen if you are actively working on this.