chore(github): document SDD workflow and issue templates in instructions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nanotaboada

.github/copilot-instructions.md

@@ -109,6 +109,25 @@ Example: `feat(api): add player stats endpoint (#42)`
 - Test database configuration (in-memory SQLite)
 - Production configurations or deployment secrets
 
+### Creating Issues
+
+This project uses Spec-Driven Development (SDD): discuss in Plan mode first, create a GitHub Issue as the spec artifact, then implement. Always offer to draft an issue before writing code.
+
+**Feature request** (`enhancement` label):
+- **Problem**: the pain point being solved
+- **Proposed Solution**: expected behavior and functionality
+- **Suggested Approach** *(optional)*: implementation plan if known
+- **Acceptance Criteria**: at minimum — behaves as proposed, tests added/updated, no regressions
+- **References**: related issues, docs, or examples
+
+**Bug report** (`bug` label):
+- **Description**: clear summary of the bug
+- **Steps to Reproduce**: numbered, minimal steps
+- **Expected / Actual Behavior**: one section each
+- **Environment**: runtime versions + OS
+- **Additional Context**: logs, screenshots, stack traces
+- **Possible Solution** *(optional)*: suggested fix or workaround
+
 ### Key workflows
 
 **Add an endpoint**: Define DTO in `models/` with Bean Validation → add service method in `services/` with `@Transactional` → create controller endpoint with `@Operation` annotation → add tests → run `./mvnw clean test jacoco:report`.