chore: fix formatting and clarify observability docs

- Fix trailing whitespace in reporter_otel_test.go
- Update observability.md to accurately reflect current implementation
- Clarify that phase durations are captured as attributes, not spans
- Move phase-level spans to future enhancements section

Co-authored-by: Ona <no-reply@ona.com>

Author: corneliusludmann

docs/observability.md

@@ -19,18 +19,14 @@ OpenTelemetry tracing in leeway captures:
 ```
 Root Span (leeway.build)
 ├── Package Span 1 (leeway.package)
-│   ├── Phase: prep
-│   ├── Phase: pull
-│   ├── Phase: lint
-│   ├── Phase: test
-│   └── Phase: build
 ├── Package Span 2 (leeway.package)
 └── Package Span N (leeway.package)
 ```
 
 - **Root Span**: Created when `BuildStarted` is called, represents the entire build operation
 - **Package Spans**: Created for each package being built, as children of the root span
-- **Phase Spans**: (Future) Individual build phases within each package
+
+Build phase durations (prep, pull, lint, test, build, package) are captured as attributes on package spans, not as separate spans.
 
 ### Context Propagation
 
@@ -298,8 +294,10 @@ Tests use in-memory exporters (`tracetest.NewInMemoryExporter()`) to verify:
 
 ## Future Enhancements
 
-- Phase-level spans for detailed timing
-- Custom span events for build milestones
-- Metrics integration (build duration histograms, cache hit rates)
-- Sampling configuration
-- Additional exporters (Zipkin, Prometheus)
+Potential improvements for future iterations:
+
+- **Phase-level spans**: Create individual spans for each build phase (prep, pull, lint, test, build, package) instead of just attributes
+- **Span events**: Add timeline events for build milestones (e.g., cache hit, dependency resolution)
+- **Metrics integration**: Export metrics alongside traces (build duration histograms, cache hit rates, concurrent build count)
+- **Sampling configuration**: Add configurable sampling strategies for high-volume builds
+- **Additional exporters**: Support for Zipkin, Jaeger native protocol, or Prometheus

pkg/leeway/reporter_otel_test.go

@@ -364,12 +364,12 @@ func TestOTelReporter_GitHubAttributes(t *testing.T) {
 		"GITHUB_SERVER_URL",
 		"GITHUB_WORKFLOW_REF",
 	}
-	
+
 	oldVars := make(map[string]string)
 	for _, key := range githubVars {
 		oldVars[key] = os.Getenv(key)
 	}
-	
+
 	defer func() {
 		for key, val := range oldVars {
 			if val == "" {