feat: make tinker-atropos RL training fully optional

The tinker-atropos submodule and its heavy dependencies (atroposlib, tinker,
wandb, fastapi, uvicorn) were being installed for all users by default,
adding significant install time and disk usage for most users who don't
need RL training capabilities.

Changes:
- install.sh: Only init mini-swe-agent submodule by default; skip
  tinker-atropos clone and install entirely
- install.sh: Remove --recurse-submodules from git clone (only fetches
  what's needed)
- pyproject.toml: Add [rl] optional dependency group for explicit opt-in
- rl_training_tool.py: Move LOGS_DIR.mkdir() from module-level to lazy
  init (_ensure_logs_dir) to avoid side effects on import
- README.md: Update contributor quick start to not auto-fetch
  tinker-atropos; add RL opt-in instructions

Users who want RL training can opt in with:
  git submodule update --init tinker-atropos
  uv pip install -e ./tinker-atropos

scripts/install.sh

@@ -572,17 +572,16 @@ clone_repo() {
         fi
     else
         # Try SSH first (for private repo access), fall back to HTTPS
-        # Use --recurse-submodules to also clone mini-swe-agent and tinker-atropos
         # GIT_SSH_COMMAND disables interactive prompts and sets a short timeout
         # so SSH fails fast instead of hanging when no key is configured.
         log_info "Trying SSH clone..."
         if GIT_SSH_COMMAND="ssh -o BatchMode=yes -o ConnectTimeout=5" \
-           git clone --branch "$BRANCH" --recurse-submodules "$REPO_URL_SSH" "$INSTALL_DIR" 2>/dev/null; then
+           git clone --branch "$BRANCH" "$REPO_URL_SSH" "$INSTALL_DIR" 2>/dev/null; then
             log_success "Cloned via SSH"
         else
             rm -rf "$INSTALL_DIR" 2>/dev/null  # Clean up partial SSH clone
             log_info "SSH failed, trying HTTPS..."
-            if git clone --branch "$BRANCH" --recurse-submodules "$REPO_URL_HTTPS" "$INSTALL_DIR"; then
+            if git clone --branch "$BRANCH" "$REPO_URL_HTTPS" "$INSTALL_DIR"; then
                 log_success "Cloned via HTTPS"
             else
                 log_error "Failed to clone repository"
@@ -593,10 +592,12 @@ clone_repo() {
 
     cd "$INSTALL_DIR"
 
-    # Ensure submodules are initialized and updated (for existing installs or if --recurse failed)
-    log_info "Initializing submodules (mini-swe-agent, tinker-atropos)..."
-    git submodule update --init --recursive
-    log_success "Submodules ready"
+    # Only init mini-swe-agent (terminal tool backend — required).
+    # tinker-atropos (RL training) is optional and heavy — users can opt in later
+    # with: git submodule update --init tinker-atropos && uv pip install -e ./tinker-atropos
+    log_info "Initializing mini-swe-agent submodule (terminal backend)..."
+    git submodule update --init mini-swe-agent
+    log_success "Submodule ready"
 
     log_success "Repository ready"
 }
@@ -679,12 +680,11 @@ install_deps() {
         log_warn "mini-swe-agent not found (run: git submodule update --init)"
     fi
 
-    log_info "Installing tinker-atropos (RL training backend)..."
+    # tinker-atropos (RL training) is optional — skip by default.
+    # To enable RL tools: git submodule update --init tinker-atropos && uv pip install -e "./tinker-atropos"
     if [ -d "tinker-atropos" ] && [ -f "tinker-atropos/pyproject.toml" ]; then
-        $UV_CMD pip install -e "./tinker-atropos" || log_warn "tinker-atropos install failed (RL tools may not work)"
-        log_success "tinker-atropos installed"
-    else
-        log_warn "tinker-atropos not found (run: git submodule update --init)"
+        log_info "tinker-atropos submodule found — skipping install (optional, for RL training)"
+        log_info "  To install: $UV_CMD pip install -e \"./tinker-atropos\""
     fi
 
     log_success "All dependencies installed"