Enhance documentation structure and clarify project domain; add new directories for architecture, contracts, and extensions; update roadmap and open questions with resolved decisions and clarification plans.

README.md

@@ -101,8 +101,19 @@ make flatpak-build
 ```
 Cargo.toml
 Cargo.lock
+docs/
+  adrs/                  # Architecture decision records
+  contracts/             # API and behavior contracts (planning artifacts)
+  extensions/            # Extension model planning and examples
+  OPEN_QUESTIONS.md
+  ROADMAP.md
+  ARCHITECTURE.md
+schemas/
+  project-core/          # Core project schema artifacts
+  extensions/            # Domain-specific extension schema artifacts
 src/
   └── main.rs (or lib.rs)
+tests/
 Makefile
 .envrc
 flake.nix
@@ -126,6 +137,7 @@ See project.toml for example metadata.
 - [Roadmap](docs/ROADMAP.md)
 - [Architecture baseline](docs/ARCHITECTURE.md)
 - [Development workflow (TDD/BDD + GitHub Flow)](docs/WORKFLOW.md)
+- [Open questions and clarification plan](docs/OPEN_QUESTIONS.md)
 
 ## Helper Tools