fix(scripts): make install_uv resilient to missing env helper (#547)

The uv installer does not always create $HOME/.local/bin/env (older
versions, or when the install is skipped), so the unconditional `source`
broke setup with `No such file or directory`. Source the helper only if
it exists, prepend $HOME/.local/bin to PATH as a fallback, and fail
loudly if `uv` is still unreachable after install.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/common.sh

@@ -92,8 +92,22 @@ install_uv() {
     print_status "Installing uv..."
     if ! command_exists uv; then
         curl -fsSL https://astral.sh/uv/install.sh | sh
-        print_status "Sourcing uv environment..."
-        source "$HOME/.local/bin/env"
+        print_status "Loading uv into PATH..."
+        # Newer uv installers drop a helper at $HOME/.local/bin/env; older
+        # ones do not. Source it when present and always ensure the install
+        # dir is on PATH so the freshly-installed binary is reachable.
+        if [ -f "$HOME/.local/bin/env" ]; then
+            # shellcheck disable=SC1091
+            source "$HOME/.local/bin/env"
+        fi
+        case ":$PATH:" in
+            *":$HOME/.local/bin:"*) ;;
+            *) export PATH="$HOME/.local/bin:$PATH" ;;
+        esac
+        if ! command_exists uv; then
+            print_error "uv install completed but 'uv' is not on PATH"
+            return 1
+        fi
         print_success "uv installed successfully"
     else
         print_success "uv is already installed"