(chore): document and test new LogLevel APIs

- add godoc for SameLevel and Equal
- update package docs and READMEs with new helpers
- refresh unreleased release notes
- add tests for Printf, HTTP method levels, and level constructors

RELEASE_NOTES.md

@@ -1,6 +1,6 @@
-# v2.2.0
+# Unreleased (planned v2.2.0)
 
-This release adds new public APIs for working with log levels, introduces HTTP method-specific log levels, and improves package documentation.
+This release expands the public LogLevel API, adds HTTP method helpers, and improves package documentation and test coverage.
 
 ### Added
 
@@ -28,15 +28,18 @@ This release adds new public APIs for working with log levels, introduces HTTP m
   - `HTTPUnknownLevel`
 - Added `LogLevelForMethod(method string) LogLevel` to map HTTP methods to predefined log levels.
 - Added `Logger.Printf(level, format, args...)` for formatted logging with an explicit log level.
+- Added `LogLevel.SameLevel` and `LogLevel.Equal` for severity-only and full level comparisons.
 
 ### Changed
 
 - Refactored log level definitions into a dedicated `levels.go` file.
 - Unified `Logger.Print` and `Logger.Println` through a shared internal implementation without changing their behavior.
+- Expanded test coverage for `Logger.Printf`, HTTP level mapping, and new level constructors.
 
 ### Documentation
 
 - Improved GoDoc coverage for exported types, constructors, formatters, colors, HTTP helpers, and time layouts.
+- Documented level comparison helpers and explicit-level formatted logging.
 - Expanded inline documentation for formatter tokens and default formatter behavior.
 
 ### Compatibility