feat: add coreex-test-api, coreex-test-subscribe, coreex-test-relay skills

[chullybun]

Summary

Adds the three integration-test skills covering the CoreEx test project types that had no first-class skill yet (only *.Test.Unit guidance was previously embedded in coreex-validator/coreex-aggregate/coreex-adapter).

• coreex-test-api — canonical *.Test.Api workflow: seed data (read-data.seed.yaml/mutate-data.seed.yaml), per-entity read/mutate test classes, CRUD/ETag/soft-delete/idempotent-delete scenarios, provider-specific outbox assertions, inter-domain HTTP mocking, resource-based JSON assertions. Owns the shared DB/cache/outbox setup foundations.
• coreex-test-subscribe — *.Test.Subscribe workflow: simulating broker message receipt via ServiceBusSubscribedSubscriber, ErrorHandler outcome assertions, and the three subscriber test shapes (command / event-data-sync / event-business-process). Links back to coreex-test-api for the shared setup mechanics rather than duplicating it.
• coreex-test-relay — lightweight *.Test.Relay skill, since relay tests are largely templated plumbing rarely extended per domain. Covers the outbox-forwarding pattern, hosted-service pause/resume checks, and the Service Bus emulator troubleshooting note.

Usage model

Both standalone invocation (consumer asks "write the API test for X") and delegation — coreex-api and coreex-subscriber now hand off to the matching test skill as their final step instead of dead-ending at coreex-tests.instructions.md directly.

Other changes

• Extracted ~154 lines of duplicated Subscribe-test guidance out of coreex-subscriber/references/workflow.md into coreex-test-subscribe, leaving a pointer behind (single source of truth, per the tests instructions' "do not duplicate" rule).
• Repointed coreex-api and coreex-subscriber SKILL.md (description + Quick Reference + Key References) to the new skills.
• Added a light hand-off pointer from solution-scaffolder.
• Wired all three new skills + prompt bridge files into CoreEx.Template.csproj (both the CoreEx.Bootstrap _AiFile set and the CoreEx.Ai per-skill Copy blocks).

Domain-agnostic

All three skills use generic {Entity}/{Domain}/YourDomain.* placeholders in their bodies, consistent with existing skills — sample links (samples/tests/Contoso.*) are kept only as illustrative Key References, not embedded in the workflow content, matching precedent set by the recent coreex-db-migration/coreex-refdata domain-agnostic cleanup.

Validation

• dotnet build src/CoreEx.Template/CoreEx.Template.csproj -c Release — succeeds (MSBuild Copy tasks fail loudly on any missing/misnamed source file, so this validates the wiring)
• Unzipped the resulting .nupkg and confirmed all 3 skills + prompts land in both content/CoreEx.Bootstrap/ and content/CoreEx.Ai/
• All new SKILL.md files are well under the 300-line cap (53 / 50 / 89 lines)

Co-authored-by: Copilot App 223556219+Copilot@users.noreply.github.com

[Copilot]

Pull request overview

Adds three new first-class CoreEx AI skills for integration test projects (*.Test.Api, *.Test.Subscribe, *.Test.Relay), updates existing skills to hand off to them, and wires the new assets into CoreEx.Template packaging so they ship in both CoreEx.Bootstrap and CoreEx.Ai.

Changes:

• Introduces coreex-test-api, coreex-test-subscribe, and coreex-test-relay skills (plus workflow refs where applicable) and their prompt bridge files.
• Refactors coreex-subscriber (and references) to point test guidance to coreex-test-subscribe; updates coreex-api to point to coreex-test-api.
• Updates template packing/copy logic so the new skills/prompts are included in generated template content.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/CoreEx.Template/CoreEx.Template.csproj	Adds the new prompts/skills to the Bootstrap _AiFile set and the CoreEx.Ai copy blocks for packaging.
.github/skills/solution-scaffolder/SKILL.md	Adds a validation-rule handoff note directing further integration-test authoring to the new test skills.
.github/skills/coreex-test-api/SKILL.md	New skill entry point for API host integration tests and shared setup foundations.
.github/skills/coreex-test-api/references/workflow.md	New detailed API test workflow (seed → tests → resources, outbox assertions, HTTP mocks).
.github/skills/coreex-test-subscribe/SKILL.md	New skill entry point for Subscribe host integration tests, linking to shared setup in coreex-test-api.
.github/skills/coreex-test-subscribe/references/workflow.md	New detailed Subscribe test workflow (message simulation, scenario-specific assertions, unsubscribed-subject test).
.github/skills/coreex-test-relay/SKILL.md	New skill guidance for Relay host tests (templated plumbing checks + troubleshooting note).
.github/skills/coreex-api/SKILL.md	Updates “When not to use” / references to hand off integration testing to coreex-test-api.
.github/skills/coreex-subscriber/SKILL.md	Removes embedded Subscribe-test guidance and redirects to coreex-test-subscribe.
.github/skills/coreex-subscriber/references/workflow.md	Replaces duplicated Subscribe-test workflow section with a pointer to coreex-test-subscribe.
.github/prompts/coreex-test-api.prompt.md	New prompt bridge for invoking coreex-test-api.
.github/prompts/coreex-test-subscribe.prompt.md	New prompt bridge for invoking coreex-test-subscribe.
.github/prompts/coreex-test-relay.prompt.md	New prompt bridge for invoking coreex-test-relay.