Add skills, instruction files, copilot-setup-steps workflow, and .java-version pin

[Copilot]

Establishes Copilot agent customization infrastructure for this repo: environment setup workflow, reusable skills, and scoped instruction files. Adds a .java-version pin (21.0.8) consumed by jenv on local machines; CI continues to use actions/setup-java.

Copilot Environment

• .github/workflows/copilot-setup-steps.yml — Pre-warms the agent with Java 21 (adopt), Gradle cache, and a dependency resolution pass against :library. Mirrors the pattern used by existing CI workflows.

Skills (.github/skills/)

• jenv-gradle-low-ram/ — Step-by-step procedure to align jenv with .java-version, run ./gradlew :library:test and :app:assembleDebug under memory pressure, with troubleshooting branches for daemon OOMs and jenv mismatches. Notes that :app is excluded when CI env var is set.
• retrofit-graphql-build-dependencies/ — Maps every build concern (SDK levels, Dokka, Spotless, versions, publishing) to its owning file; includes a references/build-map.md table.
• retrofit-graphql-kdoc-dokka/ — Per-package KDoc checklist covering annotations, converter, discovery, model, logger, and utility types; includes references/kdoc-checklist.md.
• retrofit-graphql-reference-map/ — Full package-root table for io.github.wax911.library.*, consumer entry points, and placement heuristics; includes references/module-map.md.

Instructions (.github/instructions/)

Three new files with scoped applyTo globs alongside the three existing ones:

• build-logic.instructions.md — Guidance for buildSrc, version catalog, Gradle, and workflow edits; surfaces the jenv/.java-version context and :app CI exclusion.
• context-maintenance.instructions.md — Keeps instructions, skills, and docs in sync when the codebase changes.
• kdoc-dokka.instructions.md — KDoc rules for public APIs: annotations, converter factory registration, discovery extension contracts, and logger integration.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

View in Codacy

_{TIP This summary will be updated as you push new changes. Give us feedback}