[docs](trx-rs): update docs submodule and README links for renamed pages

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

README.md

@@ -173,8 +173,8 @@ See [`examples/trx-plugin-example/README.md`](examples/trx-plugin-example/README
 
 ## Documentation
 
-- [User Manual](docs/MANUAL.md): configuration, features, and usage
-- [Architecture](docs/ARCHITECTURE.md): system design, crate layout, data flow, and internals
+- [User Manual](docs/User-Manual.md): configuration, features, and usage
+- [Architecture](docs/Architecture.md): system design, crate layout, data flow, and internals
 - [`CONTRIBUTING.md`](CONTRIBUTING.md): contribution and commit rules
 
 ## Project Status