docs(copilot): unify instructions as canonical single-file format

.github/copilot-instructions.md

@@ -1,91 +1,119 @@
 # GitHub Copilot Instructions
 
-> **Token Budget**: Target 600, limit 650 (auto-loaded)
-> Details: `#file:AGENTS.md` (~2,550 tokens, on-demand)
-> Skills: `#file:SKILLS/<name>/SKILL.md` (on-demand)
+## Overview
 
-## Quick Context
+REST API for managing football players built with ASP.NET Core 10. Implements CRUD operations with a layered architecture, EF Core + SQLite persistence, FluentValidation, AutoMapper, and in-memory caching. Part of a cross-language comparison study (Go, Java, Python, Rust, TypeScript).
 
-ASP.NET Core 10 REST API with layered architecture
-**Stack**: .NET 10 LTS, EF Core 10, SQLite, Docker, xUnit
-**Pattern**: Repository + Service + AutoMapper + FluentValidation
-**Focus**: Learning PoC emphasizing clarity and best practices
+## Tech Stack
 
-## Core Conventions
-
-- **Naming**: PascalCase (public), camelCase (private)
-- **DI**: Primary constructors everywhere
-- **Async**: All I/O operations use async/await
-- **Logging**: Serilog with structured logging
+- **Language**: C# (.NET 10 LTS)
+- **Framework**: ASP.NET Core (MVC controllers)
+- **ORM**: Entity Framework Core 10
+- **Database**: SQLite
+- **Mapping**: AutoMapper
+- **Validation**: FluentValidation
+- **Caching**: `IMemoryCache` (1-hour TTL)
+- **Logging**: Serilog (structured, console + file)
 - **Testing**: xUnit + Moq + FluentAssertions
 - **Formatting**: CSharpier
-- **Commits**: Conventional Commits with issue number suffix
-  - Format: `type(scope): description (#issue)` (max 80 chars)
-  - Types: feat, fix, chore, docs, test, refactor
-  - Example: `feat(api): add player search endpoint (#123)`
-  - Body lines ≤80 chars
+- **Containerization**: Docker
 
-## Architecture
+## Structure
 
 ```text
-Controller → Service → Repository → Database
-     ↓          ↓
-Validation  Caching
+src/Dotnet.Samples.AspNetCore.WebApi/
+├── Controllers/        — HTTP handlers; minimal logic, delegate to services        [HTTP layer]
+├── Services/           — Business logic + IMemoryCache caching                     [business layer]
+├── Repositories/       — Generic Repository<T> + specific implementations          [data layer]
+├── Models/             — Player entity + DTOs
+├── Validators/         — FluentValidation (structure only; business rules in services)
+├── Profiles/           — AutoMapper profiles
+├── Data/               — DbContext + DbInitializer
+└── Storage/            — SQLite database file
+
+test/Dotnet.Samples.AspNetCore.WebApi.Tests/
+├── ControllersTests/
+└── ServicesTests/
 ```
 
-Controllers: Minimal logic, delegate to services
-Services: Business logic + `IMemoryCache` caching
-Repositories: Generic `Repository<T>` + specific implementations
-Models: `Player` entity + DTOs
-Validators: FluentValidation (structure only, business rules in services)
-
-## Copilot Should
+**Layer rule**: `Controller → Service → Repository → Database`. Controllers must not access repositories directly. Business logic must not live in controllers.
 
-- Generate idiomatic ASP.NET Core code with minimal controller logic
-- Use EF Core async APIs with `AsNoTracking()` for reads
-- Follow Repository + Service pattern consistently
-- Write tests with xUnit/Moq/FluentAssertions
-- Apply RFC 7807 Problem Details for errors
-- Use primary constructors for DI
-- Implement structured logging with `ILogger<T>`
+## Coding Guidelines
 
-## Copilot Should Avoid
+- **Naming**: PascalCase (public members), camelCase (private fields)
+- **DI**: Primary constructors everywhere
+- **Async**: All I/O operations use `async`/`await`; no `ConfigureAwait(false)` (unnecessary in ASP.NET Core)
+- **Reads**: Use `AsNoTracking()` for all EF Core read queries
+- **Errors**: RFC 7807 Problem Details for all error responses
+- **Logging**: Structured logging via `ILogger<T>`; never `Console.Write`
+- **Tests**: xUnit + Moq + FluentAssertions; test naming mirrors method under test
+- **Avoid**: synchronous EF Core APIs, controller business logic, static service/repository classes
 
-- Synchronous EF Core APIs
-- Controller business logic (belongs in services)
-- Static service/repository classes
-- `ConfigureAwait(false)` (unnecessary in ASP.NET Core)
+## Commands
 
-## Quick Commands
+### Quick Start
 
 ```bash
-# Run with hot reload
-dotnet watch run --project src/Dotnet.Samples.AspNetCore.WebApi
+dotnet restore
+dotnet build
+dotnet run --project src/Dotnet.Samples.AspNetCore.WebApi           # https://localhost:9000
+dotnet watch run --project src/Dotnet.Samples.AspNetCore.WebApi     # hot reload
+dotnet test --settings .runsettings                                 # with coverage
+docker compose up
+```
 
-# Test with coverage
-dotnet test --settings .runsettings
+### Pre-commit Checks
 
-# Docker
-docker compose up
+1. Update `CHANGELOG.md` `[Unreleased]` section (Added / Changed / Fixed / Removed)
+2. `dotnet build --configuration Release` — must succeed
+3. `dotnet test --settings .runsettings` — all tests must pass
+4. Verify code formatting with CSharpier
+5. Commit message follows Conventional Commits format (enforced by commitlint)
 
-# Swagger: https://localhost:9000/swagger
-```
+### Commits
+
+Format: `type(scope): description (#issue)` — max 80 chars
+Types: `feat` `fix` `chore` `docs` `test` `refactor` `ci` `perf`
+Example: `feat(api): add player search endpoint (#123)`
 
-## Load On-Demand Files
+## Agent Mode
 
-**Load `#file:AGENTS.md` when:**
-- "How do I run tests with coverage?"
-- "CI/CD pipeline setup or troubleshooting"
-- "Database migration procedures"
-- "Publishing/deployment workflows"
-- "Detailed troubleshooting guides"
+### Proceed freely
 
-**Load `#file:SKILLS/<skill-name>/SKILL.md` (planned):**
-- Docker optimization: `docker-containerization/SKILL.md`
-- Testing patterns: `testing-patterns/SKILL.md`
+- Route handlers and controllers
+- Service layer logic and caching
+- Repository implementations
+- Unit and integration tests
+- Documentation and CHANGELOG updates
+- Bug fixes and refactoring within existing patterns
 
-**Human-readable overview**: See `README.md` (not auto-loaded)
+### Ask before changing
 
----
+- Database schema (entity fields, migrations)
+- Dependencies (`*.csproj`, `global.json`)
+- CI/CD configuration (`.github/workflows/`)
+- Docker setup
+- Application configuration (`appsettings.json`)
+- API contracts (breaking DTO changes)
+- Caching strategy or TTL values
 
-**Why this structure?** Base instructions (~600 tokens) load automatically. On-demand files (~2,550 tokens) load only when needed, saving 80% of tokens per chat.
+### Never modify
+
+- Production configurations or deployment secrets
+- `.runsettings` coverage thresholds
+- Port configuration (9000)
+- Database type (SQLite — demo/dev only)
+
+### Key workflows
+
+**Add an endpoint**: Add DTO in `Models/` → update `PlayerMappingProfile` in `Mappings/` (AutoMapper) → add repository method(s) in `Repositories/` → add service method in `Services/` → add controller action in `Controllers/` → add validator in `Validators/` → add tests → run pre-commit checks.
+
+**Modify schema**: Update `Player` entity → update DTOs → update AutoMapper profile → reset `Storage/players.db` → update tests → run `dotnet test`.
+
+**After completing work**: Suggest a branch name (e.g. `feat/add-player-search`) and a commit message following Conventional Commits including co-author line:
+
+```text
+feat(scope): description (#issue)
+
+Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
+```