feat: add doc-view integration for PDF viewing with zoom

PDFs now render via Kitty graphics in terminal doc-view-mode.
Pages display centered in the window with n/p navigation and
+/-/0 zoom controls.

- Advise doc-view-mode-p to bypass display-graphic-p guard
  while preserving per-type tool availability checks
- Advise doc-view-insert-image to render pages via Kitty
  using the centered display helper with zoom scale
- Advise doc-view-enlarge and doc-view-scale-reset to update
  the buffer-local scale factor and re-render

0 files changed, 0 insertions, 0 deletions