Release Pi Graph Core v0.1.0

[ali-abassi]

What changed

• refactored Core into a conventional installable src/pi_graph_core package with the piw entry point
• added zero-cost onboarding, doctor, version reporting, concise JSON/plain errors, and four published examples
• documented setup, usage, architecture, security boundary, contribution flow, and the v0.1.0 release
• strengthened durable-run, routing, recovery, installed-wheel, help/error, and ASCII terminal tests
• expanded CI across macOS/Linux and Python 3.10/3.14 with lint, clean-wheel installation, and a first-user journey

Evidence

• 28 unit/behavioral tests pass
• every example validates under strict mode
• wheel and sdist pass twine check; clean wheel install and pip check pass
• dependency audit: 0 known vulnerabilities; all runtime packages declare MIT
• Gitleaks history and working-tree scans pass; positive control was detected
• independent Luna/xhigh terminal review: all T1-T12 and TX-C1-TX-C6 pass
• final terminal surface contract validates mechanically

Release

After protected checks pass and this PR is merged, create the v0.1.0 GitHub release with the exact wheel and source archive, then verify the documented tag install in a new environment.