macos: pixel attachments, live theming, and a signed app

The AppKit shell now draws what the core renders, follows the theme without a
relaunch, and builds into something you can hand to someone.

- Pixel attachments. Surface.images was dropped on the floor here, so a PDF
  pane showed nothing at all: native_images is now set, pardes_image_s carries
  the geometry the core already clipped, and PardesView keeps one CGImage per
  (serial, page, revision) so scrolling costs a draw and not a decode. Image
  panes get real pixels instead of the petscii fallback.

- Themes take hold live. pardes_tick never advanced the chrome animation, so
  every tagline kept the previous theme's colours until the next launch and
  the 16 ms re-pump spun for the rest of the session. pardes_theme_bg retires
  the hand-agreed #121212 and drives the window background and the titlebar
  appearance; a theme with no background of its own now gets a transparent
  window over an NSVisualEffectView.

- The cell snaps to whole DEVICE pixels rather than whole points. Monaco
  advances 8.4014pt at 14, so ceiling to 9 spaced every column 7.1% wider than
  the face was drawn for.

- The dial is one notch per 10 degrees instead of 20, and a release keeps
  turning in proportion to how hard it was thrown -- ramping up from zero at
  the floor, so a slow twist coasts not a little but not at all.

- A file dropped on the grid is a click plus Look, so it opens beside the pane
  it was dropped on. No drop concept was added to the core.

- The titlebar follows the focused pane: proxy icon, filename, and the dirty
  dot. File.saved_revision is the watermark that last one needed.

- Config (SPC f c) prints the resolved startup config path.

- build.zig assembles, signs and packages the bundle itself; build-app.sh is
  gone. -Dmacos-identity= takes a Developer ID, macos-dmg makes the image, and
  the icon is Glenda.

1 files changed, 2 insertions, 2 deletions

diff --git a/test/macos-snapshots/boot.golden b/test/macos-snapshots/boot.golden
index 28e5a1de..1c971b3f 100644
--- a/test/macos-snapshots/boot.golden
+++ b/test/macos-snapshots/boot.golden
@@ -23,7 +23,7 @@
 |
 |
 |
-== draw boot 720x408 nonblank
+== draw boot 680x396 nonblank
 == snap resized grid=100x30 cursor=4,2
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
 |$ /private/tmp/pardes-macos-e2e/boot/cwd                                 New Del
@@ -55,4 +55,4 @@
 |
 |
 |
-== draw resized 900x510 nonblank
+== draw resized 850x495 nonblank