- Add ecosystem installer fallback (cargo, go) after pip fails
- Add manual install script fallback for Linux as last resort
- Add missing tools to TOOL_PACKAGES: gitleaks, trivy, checkov, jsonlint, semgrep
- Add kube-linter manual install for Linux
- Add gitleaks and kube-linter to ECOSYSTEM_MAP for go install
- Fix taplo, hadolint, gitleaks, trivy installation on Linux

This fixes the bug where tools failed with "Not available in apt" and
then "no installers available" instead of trying ecosystem or manual
install methods.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>