v0.9.0

What's Changed

• docs(amkb): mark v0.7.0/v0.7.1 as shipped by @takyone in #60
• ci(docs): clone amkb-sdk sibling before uv sync by @takyone in #61
• build(workspace): pin amkb via git source, drop sibling checkout by @takyone in #62
• docs(amkb): add 4 theory appendices by @takyone in #64
• docs(design): Stage 1 tutor-extraction contract design by @takyone in #67
• refactor(tutor): extract spikuit-tutor package — Stage 0 boundary move by @takyone in #66
• feat(appkit): Stage 1 — spikuit_core.appkit contract facade by @takyone in #68
• docs(design): Spikuit/AMKB roadmap + substrate self-organization by @takyone in #65
• docs: Stage 2 (DB migration) design by @takyone in #69
• Tutor extraction Stage 2 — retire FSRS from spikuit-core (v0.9.0) by @takyone in #70
• fix(docs): repoint mkdocstrings directives off retired spikuit_core symbols by @takyone in #71

Full Changelog: v0.7.1...v0.9.0