install: guide user to update PATH for current shell session

When copilot is not on PATH after install, the script now:
- Tells users to restart their shell or source their RC file after
  adding the PATH export
- Provides a copy-pasteable one-liner (export PATH + copilot help)
  that fixes PATH for the current session and runs the getting started
  command
- Only shows the simple 'copilot help' message when it will actually
  work

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: devm33

install.sh

@@ -156,14 +156,19 @@ if ! command -v copilot >/dev/null 2>&1; then
       if [ "$REPLY" = "y" ] || [ "$REPLY" = "Y" ]; then
         echo "export PATH=\"$INSTALL_DIR:\$PATH\"" >> "$RC_FILE"
         echo "✓ Added PATH export to $RC_FILE"
+        echo "  Restart your shell or run: source $RC_FILE"
       fi
     fi
   else
     echo ""
     echo "To add $INSTALL_DIR to your PATH permanently, add this to $RC_FILE:"
     echo "  export PATH=\"$INSTALL_DIR:\$PATH\""
   fi
-fi
 
-echo ""
-echo "Installation complete! Run 'copilot help' to get started."
+  echo ""
+  echo "Installation complete! To get started, run:"
+  echo "  export PATH=\"$INSTALL_DIR:\$PATH\" && copilot help"
+else
+  echo ""
+  echo "Installation complete! Run 'copilot help' to get started."
+fi