docs: keep product documentation public, relocate engineering material

[Ndevu12]

The public repository now carries product and marketing documentation only. Everything removed here
is preserved in the private engineering repository — nothing was discarded. Paired with
Ndevu12/saw#1.

Removed (internal end to end)

docs/ARCHITECTURE.md, docs/SECURITY_ARCHITECTURE.md, docs/RELEASING.md, CLAUDE.md,
.claude/skills/ (8 skills), .claude/settings.json, and public/stayawakebot_architecture.svg,
whose embedded text rendered the internal module layout.

Redacted in place, user-facing content kept

File	What came out
README.md	detection-technique enumeration, the ## Architecture heading, the provenance rationale note, links to relocated docs, and a real org name in an example
docs/CLI.md	the design-rationale appendix
docs/USAGE.md	the explanation of what a normal scan does not cover
CONTRIBUTING.md	layering rule, module tree, principles, signature and bot authoring steps
prevent/SECURITY_BASELINE.md	token hardening and recovery sections
.github/CODEOWNERS	rationale comments — the ownership rules are unchanged and still functional

Install, usage, configuration, the CLI reference and licensing are unaffected. docs/PREREQUISITES.md
is untouched and is now linked from the README's documentation list.

Inbound links to relocated files were repaired in CONTRIBUTING.md, docs/CONFIGURATION.md,
docs/CREDENTIAL_HYGIENE.md, docs/USAGE.md and .github/workflows/release.yml, so no dangling
reference remains.

Deliberately left for a follow-up

• CHANGELOG.md — ~73% of its 172 entries carry internal detail and it belongs in the private
  repo, but removing it breaks .github/scripts/check_changelog_release.py, the pyproject.toml
  sdist allowlist and tests/test_changelog_release.py. It needs a thin public replacement in the
  same change.
• config/security.yml — its allowlist is a published index of signature IDs and their
  suppression paths, but CI consumes the file, so it is being analysed separately.
• pyproject.toml sets readme = "README.md", so this trim does not reach PyPI until the next
  release republishes the long description.