[feat] build log screenshot tool

[GangGreenTemperTatum]

Summary

This PR adds a small multimedia logging surface to the web-security capability so agents can attach existing local proof-of-concept media to the current Dreadnode run in the same general style as the old v1 web-agent log_screenshot helper.

The new toolset adds four path-based tools:

• log_image_output
• log_audio_output
• log_video_output
• log_file_artifact

This keeps the interface simple for the agent. When another tool has already written a file to disk, the agent can log it directly as typed media output or upload it as a raw artifact without re-implementing SDK details inside prompts or ad hoc scripts.

Why

The older Dreadnode web agent exposed a dedicated screenshot-ingest helper. The current SDK has broader primitives (Image, Audio, Video, log_output, log_artifact), but web-security did not yet expose a purpose-built tool for agents to use them consistently.

Without this wrapper, an agent would need to rely on implicit SDK knowledge or custom Python/Bash glue every time it wanted to attach a screenshot, audio clip, video, or supporting file to a run. This PR gives the capability a narrow, explicit, path-based interface for that workflow.

Changes

• add capabilities/web-security/tools/media_logging.py
• add capabilities/web-security/tests/test_media_logging.py
• extend the dreadnode test stub in capabilities/web-security/tests/conftest.py to cover typed media logging primitives
• document the new tools in capabilities/web-security/agents/web-security.md

Validation

I validated the change in a clean worktree on ads/cap-985-build-log_screenshot-tool based on fresh origin/main.

Checks run:

• python3 -m pytest capabilities/web-security/tests/test_media_logging.py capabilities/web-security/tests/test_dns_rebinding.py capabilities/web-security/tests/test_credence.py capabilities/web-security/tests/test_phone_verification.py
• pre-commit run --files capabilities/web-security/tools/media_logging.py capabilities/web-security/tests/test_media_logging.py capabilities/web-security/tests/conftest.py capabilities/web-security/agents/web-security.md
• just validate

Results:

• pytest passed: 68 passed
• pre-commit passed, including ruff and ruff-format
• just validate completed with 0 failed

Repo-level validation still shows pre-existing warnings for unrelated capabilities and local environment checks (caido-cli, Burp jar, Java 17 for Ghidra, and bloodhound-enterprise runtime import warnings). Those are not introduced by this PR.

Linear

• CAP-986