Drawer behaviors (progressive enhancement, <dialog>, shortcut, URL hash sync)

Acceptance Criteria

• On page load, for each .rf-drawer element: enhance into a <dialog> (or wrap/move accordingly — implementation detail, contract is no-JS-visible / JS-hidden); reveal the close button (hidden removed)
• Query for a[data-target-type="drawer"] whose href="#drawer-{id}" matches a drawer on this page; attach click interceptor that calls event.preventDefault() and dialog.showModal()
• Esc key closes the panel (native dialog behavior)
• Backdrop click closes the panel (event.target === dialog)
• Close button click closes the panel
• Keyboard shortcut opens the panel; skipped when focus is in input/textarea/select/contenteditable
• Shortcut parser supports bare keys and modifier prefixes (cmd+, ctrl+, alt+, shift+)
• Multiple drawers with the same shortcut emit a dev-mode warning naming both rune locations; last-registered wins
• URL hash sync: on page load, if location.hash === "#drawer-{id}", the drawer opens automatically
• Opening a drawer updates location.hash via replaceState; closing clears it
• Browser back button closes an open drawer when the open-action set the hash
• Opening one drawer while another is open closes the first (matches native <dialog> single-modal semantics; browsers enforce this)
• Authoring docs cover the xref-as-trigger pattern, progressive enhancement model, keyboard shortcut conventions, and the data-target-type convention as a primitive available to other runes