Review SCM files and security updates

[hyperpolymath]

• Replace tag-based action versions with SHA-pinned commits for security
  • actions/checkout@v4.3.1 (34e114876b0b11c390a56381ad16ebd13914f8d5)
  • actions/setup-node@v4.4.0 (49933ea5288caeca8642d1e84afbd3f7d6820020)
  • github/codeql-action@v4.31.9 (5d4e8d1aca955e8d8589aabd499c5cae939e33c7)
• Fix SECURITY.md with actual version info (was placeholder template)
• Fix dependabot.yml with proper npm and github-actions ecosystems
• Fix codeql.yml with working language matrix and build steps
• Update STATE.scm: primary-language guile -> rescript
• Update META.scm: languages unknown -> rescript
• Update ROADMAP.adoc with current completion status
• Add SPDX headers to workflows missing them

[github-advanced-security]

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