Migration

Upgrade guides and per-release migration notes.

• v0.9.1 -> v0.9.2 migration guide -- Task-v2/task-v3 to task source v4 conversion, the durable-v4-family workflow boundary at executable irVersion: 5, and release behavior changes
• v0.9.2 release note -- Self-contained terminal upgrade summary shipped for akm help migrate 0.9.2
• v0.9.16 release note -- Source-bound scheduler grants, local execution authority, and split unsafe overrides
• v0.9.17 release note -- Consolidate's retire proposals and index layout 26, replacing the LLM entity graph with declared links, and akm improve scoped to what retrieval actually returns
• v0.9.19 release note -- akm improve scoped to the bundle it writes to (scheduled runs need one --bundle run per other bundle), akm proposal reopen and the retire-proposal diff, and fewer repeat consolidate promotions
• v0.8 -> current v0.9 migration guide -- Package upgrade with fresh current config/state and explicit task conversion
• v0.7 -> v0.8 migration guide -- Task schema and 0.8-era changes
• v0.5 -> v0.6 migration guide -- Terminology cut, registry schema v3, publisher changes
• Release notes -- The short per-release notes akm help migrate <version> prints (bundled with the npm package)