Update engineering documentation runbooks

[cursor]

Summary

• Updated root README quick commands, S4R deck count, CI/gitleaks wording, and SA-S4R package workflow note.
• Expanded CONFIGURATION Makefile target catalog for verify/demo-prep/cloud-bootstrap/S4R NK/Marp targets, including local-only business-case constraints.
• Added Cursor Cloud bootstrap pointer to INSTALLATION and docs index.
• Updated DEVELOPER_GUIDE maintenance matrix for cloud bootstrap, Marp slides, packaging, and secret scanning.
• Added docs/SECURITY secret-scanning guidance and aligned S4R agent docs with the current 26-slide deck.

Codepaths covered

• Makefile targets: verify, demo-prep, cloud-bootstrap, s4r-attack-nk-*, marp-*.
• scripts/cloud-bootstrap.sh Cursor Cloud bootstrap flow.
• scripts/require-bizcase-slides.sh guarded local-only business-case slide sources.
• .github/workflows/ci.yml, .pre-commit-config.yaml, .gitleaks.toml secret/lint workflow.
• .github/workflows/package-s4r.yml SA-S4R packaging exclusions.
• demo-slides/s4r-demo-slides.md / demo-slides/README.md 26-slide presenter deck.

Knowledge gaps addressed

• Stale 19-slide references after the S4R deck expanded to 26 slides.
• Missing install-path guidance for Cursor Cloud bootstrapping.
• Incomplete Makefile target documentation for verification, demo prep, Marp, and guarded local-only bizcase exports.
• README/security/developer docs lagging behind gitleaks, package release, and doc-maintenance workflows.

Verification

• pre-commit run --all-files