docs: add changelog and breaking-changes note for ControlDependence trait family

Author: ocots

BREAKINGS.md

@@ -26,6 +26,15 @@ This document outlines all breaking changes introduced in CTBase v0.18.0-beta co
 - `NotStored` / `NotStoredType` are unchanged and remain extraction-internal to
   `CTBase.Options` (the defining file was renamed `not_provided.jl` → `not_stored.jl`).
 
+## Non-breaking note (0.25.0-beta)
+
+- **Traits**: New `ControlDependence` family added for encoding control presence in optimal control problems
+  - **New trait family**: `ControlDependence` with tags `ControlFree` and `WithControl`
+  - **Opt-in contract**: types implement `has_control_dependence_trait` and `control_dependence`
+  - **Derived predicates**: `is_control_free(obj)` and `has_control(obj)`
+  - **Internal refactoring**: shared helpers for strict-contract error handling reduce duplication
+  - **No breaking changes**: Purely additive. Existing code unaffected. New trait enables dispatch in downstream packages (CTModels, CTFlows).
+
 ## Non-breaking note (0.24.0-beta)
 
 - **Differentiation module**: Added comprehensive AD backend infrastructure for computing gradients

CHANGELOG.md

@@ -0,0 +1,33 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+## Unreleased (0.25.0-beta)
+
+### Added
+
+- **Traits**: New `ControlDependence` trait family for encoding control presence in optimal control problems
+  - Tags: `ControlFree` (no control) and `WithControl` (with control input)
+  - Opt-in contract: implement `has_control_dependence_trait` and `control_dependence`
+  - Derived predicates: `is_control_free` and `has_control`
+  - Enables downstream dispatch in CTFlows and CTModels for control-problem routing
+
+### Changed
+
+- **Traits**: Refactored strict-contract machinery to eliminate duplication
+  - New internal helpers: `_throw_missing_trait` and `_throw_trait_not_implemented`
+  - Generalised `_caller_function_name` stacktrace filter for any `has_<family>_trait` predicate
+  - All strictfamilies (time-dependence, variable-dependence, mutability, control-dependence) now share the same error handling
+  - Collapsed `has_variable` duplicate to direct alias of `is_variable`
+
+- **Documentation**: Updated Traits guide to document the two trait templates (strict opt-in vs default-valued capability)
+
+### Fixed
+
+- **Traits**: API reference now includes `control_dependence.jl` in auto-generated documentation
+
+---
+
+## Previous versions
+
+See git history and release notes for earlier versions.