Release Compass 0.1.5 for macOS and Linux

[forhappy]

Summary

• bump the Compass workspace to 0.1.5
• publish stable per-architecture macOS and Linux GNU archives with checksums and provenance
• extend the one-line installer to Apple Silicon/ARM64 and Intel/AMD64 on both operating systems
• prefer sha256sum on Linux while retaining shasum compatibility
• update README and getting-started installation guidance

Validation

• release-script syntax and behavioral tests pass for all four targets
• workflow YAML parses successfully
• locked workspace metadata resolves only version 0.1.5
• Compass product contract: 5 passed
• optimized Apple Silicon build and packaged archive verified as compass 0.1.5
• graphify update . completed (generated graph remains local)

Existing main baseline

The full workspace suite still has the pre-existing help catalog count failure (36 actual vs 35 expected) already present in origin/main CI run 30137859831. This PR changes no Rust source; the release workflow's focused product and script checks pass.