Design review: contrib adapter policy and support tiers

[aatuh]

Context

Contrib adapters and integrations are maintained outside the stable core API promise. Supported-adapter status should be useful to adopters without implying root-module stability.

Review paths

• ROADMAP.md
• docs/contrib-adapters.md
• docs/adapter-maturity.md
• docs/package-classification.tsv
• docs/supported-adapter-contracts.tsv
• docs/supported-adapter-test-realism.tsv
• VERSIONING.md

Questions

• Are supported-adapter, experimental, wrapper-only, generated, and tooling tiers clear enough?
• What evidence should be required before promoting an adapter to supported-adapter?
• Is the contrib drift policy strong enough without overstating compatibility guarantees?
• Which contrib adapters need clearer production caveats or external-service realism evidence?

Desired outcome

A recommendation for contrib support policy, including any tier wording, evidence, or release-review changes needed before broader adoption.