test(core): simplify provider test fixtures

[kitlangton]

Why
Provider tests still provisioned services they never consumed and constructed complete catalog records only to copy a few fields into the real draft. Canonical-binding tests also retained nested service reads and renamed imports, obscuring the actual test boundary.

What Changes

• Removes unused AISDK reads from six provider activation helpers and unused Plugin reads from their behavior cases.
• Updates Bedrock, Anthropic, Azure, and OpenAI catalog drafts directly with only the fields each scenario supplies.
• Binds Azure and Cloudflare Workers integration services before use.
• Uses Bun’s canonical test export in the Snowflake transport cases and the canonical test-host export in Promise adapter cases.
• Preserves all provider matrices, explicit overrides, environment boundaries, and assertions.

Scope
This owns the still-unowned TESTP-04, TESTP-06, and TESTP-08 occurrences in these eight files. #45635, #45656, #45669, #45689, and #45721 own the other accepted occurrences; only provider-openai.test.ts overlaps #45656 at the file level, with this PR changing catalog setup while #45656 changes activation/integration binding, so there is no dependency. Selector sentinels and Vertex transport injection remain separate follow-ups. Test-only refactoring requires no changeset.

Verification

cd packages/core
bun run test test/plugin/promise.test.ts test/plugin/provider-amazon-bedrock.test.ts test/plugin/provider-anthropic.test.ts test/plugin/provider-azure.test.ts test/plugin/provider-cloudflare-workers-ai.test.ts test/plugin/provider-openai-compatible.test.ts test/plugin/provider-openai.test.ts test/plugin/provider-snowflake-cortex.test.ts
bun typecheck

cd ../..
bun oxlint packages/core/test/plugin/promise.test.ts packages/core/test/plugin/provider-amazon-bedrock.test.ts packages/core/test/plugin/provider-anthropic.test.ts packages/core/test/plugin/provider-azure.test.ts packages/core/test/plugin/provider-cloudflare-workers-ai.test.ts packages/core/test/plugin/provider-openai-compatible.test.ts packages/core/test/plugin/provider-openai.test.ts packages/core/test/plugin/provider-snowflake-cortex.test.ts
bun prettier --check packages/core/test/plugin/promise.test.ts packages/core/test/plugin/provider-amazon-bedrock.test.ts packages/core/test/plugin/provider-anthropic.test.ts packages/core/test/plugin/provider-azure.test.ts packages/core/test/plugin/provider-cloudflare-workers-ai.test.ts packages/core/test/plugin/provider-openai-compatible.test.ts packages/core/test/plugin/provider-openai.test.ts packages/core/test/plugin/provider-snowflake-cortex.test.ts
git diff --check origin/v2...HEAD
git push -u origin provider-test-cleanup

All 88 focused tests passed. Core and push-hook workspace typechecks passed. Formatting and diff checks passed. Scoped lint reported zero errors and only 13 pre-existing fixture assertion/control-flow warnings.