docs: add CONTRIBUTORS.md and CHANGELOG.md entry for architecture overview PR

- Add CleverThis to CONTRIBUTORS.md contributor list
- Add CHANGELOG.md entry under [Unreleased] for architecture documentation update
  (A2A protocol overview, storage/persistence, LangGraph execution, TUI architecture,
  server roadmap, and milestone progress)

Closes #8763

CHANGELOG.md

@@ -17,6 +17,8 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Added
 
+- **Architecture Overview Documentation**: Expanded A2A protocol overview with JSON-RPC envelopes, event streaming, and remote transport; documented storage/persistence, LangGraph execution, TUI architecture, server roadmap, and milestone progress.
+
 - **TDD Issue-Capture Test Activation** (#7025): Replaced 234 bare `@skip` tags
   across 82 Behave feature files with the correct `@tdd_expected_fail @tdd_issue
   @tdd_issue_<N>` tag system. Scenarios whose referenced bugs were already fixed

CONTRIBUTORS.md

@@ -2,6 +2,7 @@
 
 * Aditya Chhabra <aditya.chhabra@cleverthis.com>
 * Brent E. Edwards <brent.edwards@cleverthis.com>
+* CleverThis
 * HAL 9000 <hal9000@cleverthis.com>
 * Hamza Khyari <hamza.khyari@cleverthis.com>
 * Jeffrey Phillips Freeman <jeffrey.freeman@syncleus.com>