📝 docs: cherry-pick 6 focused guides from PR #17 (CLI, CODE_EXAMPLES, HISTORY, OBSERVABILITY, ROADMAP, TROUBLESHOOTING)

documentation/CODE_EXAMPLES.md

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+# Code Examples
+
+Snippets and patterns used across the `dance-lessons-coach` codebase. Extracted from the original `AGENTS.md` (Tâche 6 restructure).
+
+## Adding a New API Endpoint
+
+```go
+// 1. Add to interface
+func (h *apiV1GreetHandler) RegisterRoutes(router chi.Router) {
+    router.Get("/", h.handleGreetQuery)
+    router.Get("/{name}", h.handleGreetPath)
+    router.Post("/custom", h.handleCustomGreet) // New endpoint
+}
+
+// 2. Implement handler
+func (h *apiV1GreetHandler) handleCustomGreet(w http.ResponseWriter, r *http.Request) {
+    // Parse request
+    // Call service
+    // Return JSON response
+}
+```
+
+## Logging with Zerolog
+
+```go
+// Trace level logging
+log.Trace().Ctx(ctx).Str("key", "value").Msg("message")
+
+// Info level
+log.Info().Msg("Important event")
+
+// Error level
+log.Error().Err(err).Msg("Error occurred")
+```
+
+For the full logging strategy (when to use Trace vs Info, performance considerations), see [ADR-0003 — Zerolog Logging](../adr/0003-zerolog-logging.md).
+
+## Using `context.Context`
+
+```go
+// Pass context through calls
+func handler(w http.ResponseWriter, r *http.Request) {
+    result := service.Greet(r.Context(), "John")
+    // ...
+}
+
+// Create context with values
+ctx := context.WithValue(r.Context(), "key", "value")
+
+// Create context with timeout
+ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
+defer cancel()
+```
+
+For the rationale behind context-aware services, see [ADR-0004 — Interface-Based Design](../adr/0004-interface-based-design.md).
+
+## Best Practices Reminders
+
+For higher-level guidance on code organization, error handling, performance, and testing, see [`AGENT_USAGE_GUIDE.md`](AGENT_USAGE_GUIDE.md#best-practices) section "Best Practices".