docs: add architecture.jpeg diagram, update README reference

- Add final architecture diagram (architecture.jpeg)
- Update README to reference architecture.jpeg instead of docs/architecture.svg
- Add .DS_Store to .gitignore

657 tests passing, 0 clippy warnings, cargo fmt clean

.gitignore

@@ -1,3 +1,4 @@
 /target
 *.db
 *.db-journal
+.DS_Store

README.md

@@ -55,7 +55,7 @@ cargo run --release -- tools test memory_recall '{"query": "Rust"}'
 Every subsystem is a **trait** — swap implementations with a config change, zero code changes.
 
 <p align="center">
-  <img src="docs/architecture.svg" alt="ZeroClaw Architecture" width="800" />
+  <img src="architecture.jpeg" alt="ZeroClaw Architecture" width="800" />
 </p>
 
 | Subsystem | Trait | Ships with | Extend |