Promote doctor check in onboarding docs

USAGE.md

@@ -1,6 +1,20 @@
 # Claw Code Usage
 
-This guide covers the current Rust workspace under `rust/` and the `claw` CLI binary.
+This guide covers the current Rust workspace under `rust/` and the `claw` CLI binary. If you are brand new, make the doctor health check your first run: start `claw`, then run `/doctor`.
+
+## Quick-start health check
+
+Run this before prompts, sessions, or automation:
+
+```bash
+cd rust
+cargo build --workspace
+./target/debug/claw
+# first command inside the REPL
+/doctor
+```
+
+`/doctor` is the built-in setup and preflight diagnostic. Once you have a saved session, you can rerun it with `./target/debug/claw --resume latest /doctor`.
 
 ## Prerequisites
 
@@ -10,17 +24,25 @@ This guide covers the current Rust workspace under `rust/` and the `claw` CLI bi
   - `claw login` for OAuth-based auth
 - Optional: `ANTHROPIC_BASE_URL` when targeting a proxy or local service
 
-## Build the workspace
+## Install / build the workspace
 
 ```bash
 cd rust
 cargo build --workspace
 ```
 
-The CLI binary is available at `rust/target/debug/claw` after a debug build.
+The CLI binary is available at `rust/target/debug/claw` after a debug build. Make the doctor check above your first post-build step.
 
 ## Quick start
 
+### First-run doctor check
+
+```bash
+cd rust
+./target/debug/claw
+/doctor
+```
+
 ### Interactive REPL
 
 ```bash