Bump Opengrep to v1.30.0

[lolgab]

Summary

• Bump .tool_version and the Dockerfile OPENGREP_VERSION ARG to v1.30.0 (in lock-step).
• Note in the README that opengrep/opengrep-rules is archived and its release branch no longer exists — the existing commit pin in internal/docgen/parsing.go already matches that repo's frozen main HEAD, so no code change was needed there, just doc updates so future agents don't chase a dead branch.

Test plan

• go run ./cmd/docgen completes without errors
• go test $(go list ./... | grep -v /docs/) passes
• docker build --build-arg TOOL_VERSION=$(cat .tool_version) -t codacy-opengrep:latest . succeeds, binary reports 1.30.0
• codacy-plugins-test pattern suite passes locally
• codacy-plugins-test multiple suite passes locally

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

View in Codacy

AI Reviewer: first review requested successfully. AI can make mistakes. Always validate suggestions.

_{TIP This summary will be updated as you push new changes.}

[codacy-production]

Pull Request Overview

No merge-blocking issues were identified. Codacy reports the changes are up to standards, with no new issues or complexity findings. Required validation evidence is not present in the supplied changes, so the release alignment and documentation updates should be verified by running the listed tests.

Test suggestions

• Verify .tool_version and Dockerfile OPENGREP_VERSION resolve to the same Opengrep release.
• Run the documentation generator successfully against the frozen rules pin.
• Build the Docker image and verify the bundled binary reports Opengrep 1.30.0.
• Run the Go unit test suite excluding /docs/.
• Run the codacy-plugins-test pattern and multiple suites against the built image.

Prompt proposal for missing tests

Consider implementing these tests if applicable:
1. Verify `.tool_version` and Dockerfile `OPENGREP_VERSION` resolve to the same Opengrep release.
2. Run the documentation generator successfully against the frozen rules pin.
3. Build the Docker image and verify the bundled binary reports Opengrep 1.30.0.
4. Run the Go unit test suite excluding `/docs/`.
5. Run the `codacy-plugins-test` `pattern` and `multiple` suites against the built image.

Low confidence findings

• The PR's required validation commands are not evidenced by the supplied changes; please run and record the documented generator, Go, Docker, and plugin test suites.

_{TIP Improve review quality by adding custom instructions
TIP How was this review? Give us feedback}