fix(context): remove duplicate ContextStrategy changelog entry (#8616) from CHANGELOG.md

The [Unreleased] section had two bullet points describing the same ContextStrategy +
StrategyRegistry feature (references #10590 and #8616). Kept the comprehensive
#10590 entry. Removed the redundant #8616 entry to ensure one Added section with
unique entries per Keep a Changelog format.

This is the final compliance fix for PR #10590 — all lint violations (F401 unused
imports), changelog duplication, and contributor duplication have been resolved.

ISSUES CLOSED: #8616, #10590

CHANGELOG.md

@@ -23,8 +23,6 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
   MappingProxyType coercion validators, thread-safety under concurrent access, boundary value
   validation via Pydantic model constraints, and per-strategy config updates.
 
-- **ContextStrategy protocol and StrategyRegistry plugin registration system** (#8616): Implemented the pluggable context assembly strategy protocol (`ContextStrategy`) with proper type-safe method signatures (`can_handle(request, backends) -> confidence`, `assemble(request, backends, budget, plan_context) -> fragments`). Added `StrategyRegistry` -- the central thread-safe registry for registration, lookup, discovery (via entry points), and per-strategy configuration (`timeout_seconds`, `max_fragments`, `max_workers`, `circuit_breaker_threshold`, `resource_types`, `extra`). Six built-in strategies implemented per spec: `simple-keyword` (0.3), `semantic-embedding` (0.6), `breadth-depth-navigator` (0.85), `arce` (0.95 -- multi-modal text+vector+graph), `temporal-archaeology` (0.5 -- historical discovery), and `plan-decision-context` (0.7 -- parent plan decision retrieval). Full BDD test coverage validating protocol conformance, registry CRUD operations, entry-point discovery, error handling, thread safety, and boundary validation.
-
 - Fixed `ReactiveEventBus.emit()` exception handler to log the full exception
   message (`str(exc)`) and enable traceback forwarding (`exc_info=True`).
   Previously the handler logged only the exception type name (e.g.