Simplify README message and onboarding

[pate0304]

Summary

• lead with the project outcome and intended audience
• replace the long onboarding path with three explicit activation steps
• explain primary-agent control, dynamic team sizing, and the 111 primitive library
• consolidate safety, documentation, status, and contribution guidance
• regenerate the source checksum manifest

Validation

• npm run check (20 test files, 140 tests)
• npm run archive:verify
• npm run sbom:verify
• npm run checksums:verify
• repository and deterministic-build validators
• npm audit --audit-level=high
• 26 local README links and anchors verified
• independent message and technical-truth reviews passed

Scope

README and its generated checksum entry only. No runtime, release, marketplace, or global configuration changes.