Complete copick-mcp documentation, artifact gates, and 2.0 release #57

Parent epic: #52

Objective

Complete copick-mcp compatibility documentation, exact-commit artifact gates, published alpha validation, and coordinated promotion to stable 2.0.

Prerequisite

• Installed transport, optional torch, and release-gating backend validation are complete.

Work

• Document Python/upstream floors, legacy readability, upstream OME-Zarr 0.5 / Zarr v3 writer policy, MCP's metadata-only boundary, complete plugin groups, verified backends, and optional torch behavior.
• Validate representative embedded nnUNet command paths/options against exact installed torch-alpha entry points without executing them.
• Inspect wheel/source contents, dependency metadata, all three setup entry points, and lockfile inclusion.
• Reuse the test workflow against Release Please's exact released SHA.
• Build distributions once after validation, inspect them once, upload them once, and publish the same artifacts using matching artifact-action majors.
• Add stable successful test contexts to active v2.0 ruleset 21015564; keep pull-request tests unfiltered so documentation-only changes report required checks.
• Publish copick-mcp 2.0.0-alpha.1 from the prerelease-only v2.0 configuration.
• Publish a later alpha.N whenever the migration branch changes and rerun the installed matrix.
• Record one exact published ecosystem prerelease set, including core, utilities, optional torch, MCP, and other migrated packages.
• Synchronize v2.0 with current main; if artifacts change, publish/revalidate a new alpha set.
• After the exact ecosystem alpha set passes, freeze implementation and stage only stable floors/version/changelog/release configuration.
• During the coordinated cutover, use >=2.0.0,<3 upstream floors and publish stable packages in dependency order.
• Run an installed-stable confirmation smoke after publication; it does not replace the prerelease gate.

Acceptance criteria

• Documentation distinguishes upstream readable input, upstream writer policy, and MCP metadata behavior.
• Exact released commits pass the locked matrix.
• Inspected artifacts are exactly the artifacts published.
• The active v2.0 ruleset requires stable migration test contexts.
• The published MCP alpha passes the same installed matrix as source.
• One recorded exact ecosystem alpha set passes after every affected code change.
• Stable metadata cannot resolve alpha or pre-2.0 copick-family packages.
• Stable release configuration is enabled only during the coordinated ecosystem cutover.
• Server Message Block remains excluded from the release definition of done.