v0.9.8

Release 0.9.8 aligns the public documentation, onboarding, capability inventory, Rust extension typing contract, release-readiness coverage gate, and source metadata for the current scpn-quantum-control source state.\n\nHighlights:\n- Added public onboarding for project purpose, user routes, application lanes, commercial route, and claim boundaries.\n- Refreshed README, documentation index, quickstart, tutorials, notebook guide, API overview, examples guide, installation guide, MkDocs navigation, and release-readiness documentation.\n- Regenerated capability manifest and README capability snapshot.\n- Aligned scpn-quantum-engine Cargo metadata with the Python package metadata.\n- Updated Rust extension typing stubs for exported AD kernels.\n\nValidation before release:\n- Local docs strict build passed.\n- Local Rust metadata check passed.\n- Local release-readiness focused tests passed.\n- Remote main workflows for commit a68dcf4 completed successfully: CI, Docs Strict Build, Deploy docs, Pre-commit, CodeQL, Docker, SBOM, Link Check, OpenSSF Scorecard, and Commit Authorship Audit.