skeleton: GtkApplication, window, GSettings schema, desktop, tests (ft0)

M0 (task ft0): the app shell — no feature views yet (those are M1 large, M7
grid).

- src/main.c: g_application_run + --version via handle-local-options (--help
  is GApplication's own); exits before activate so --version works headless.
- src/app.{c,h}: GgazeApp : AdwApplication : GtkApplication (libadwaita
  styling, decision #29), single-instance (decision #32),
  G_APPLICATION_HANDLES_OPEN; activate + open reuse the active window
  (replace-on-new-open); ggaze_window_open remembers the GFile.
- src/window.{c,h}: GgazeWindow : GtkApplicationWindow with AdwHeaderBar and a
  GtkStack (children 'grid'/'large', default 'grid'); dispose clears the file.
- data/org.buetow.ggaze.desktop (image/* MIME, validated) and
  data/org.buetow.ggaze.gschema.xml (all keys + defaults, --strict clean).
- meson: libggaze static lib shared by the executable and tests; install to
  bindir/applications/glib-2.0 schemas; gnome.post_install compiles schemas +
  updates desktop db.
- tests: unit test_app (--version/--help/unknown via subprocess), integration
  test_window (offscreen stack checks + open-titles), bootstrap. 3/3 green.
- docs/tech-stack.md: window-geometry shape corrected to (width,height,
  fullscreen,maximized) to match the schema.

4 files changed, 134 insertions, 0 deletions

diff --git a/data/.gitkeep b/data/.gitkeep
deleted file mode 100644
index e69de29..0000000
--- a/data/.gitkeep
+++ /dev/null
diff --git a/data/meson.build b/data/meson.build
new file mode 100644
index 0000000..c12b619
--- /dev/null
+++ b/data/meson.build
@@ -0,0 +1,15 @@
+# ggaze data: .desktop entry + GSettings schema. Full AppStream/icon install
+# lands in M10; this wires the basics so `meson install` lays out the app and
+# compiles the schema. gnome.post_install also refreshes the desktop database.
+
+install_data('org.buetow.ggaze.desktop',
+   install_dir : join_paths(get_option('datadir'), 'applications'))
+
+install_data('org.buetow.ggaze.gschema.xml',
+   install_dir : join_paths(get_option('datadir'), 'glib-2.0', 'schemas'))
+
+gnome = import('gnome')
+gnome.post_install(
+   glib_compile_schemas : true,
+   update_desktop_database : true,
+)
\ No newline at end of file
diff --git a/data/org.buetow.ggaze.desktop b/data/org.buetow.ggaze.desktop
new file mode 100644
index 0000000..c5c31d0
--- /dev/null
+++ b/data/org.buetow.ggaze.desktop
@@ -0,0 +1,13 @@
+[Desktop Entry]
+Type=Application
+Name=ggaze
+GenericName=Image Viewer
+Comment=Fast native image viewer for culling camera shoots
+# M0 stub; full MIME/keywords/AppStream wiring lands in M10.
+Exec=ggaze %f
+Icon=ggaze
+Terminal=false
+StartupNotify=true
+Categories=Graphics;Viewer;Photography;
+MimeType=image/png;image/jpeg;image/gif;image/webp;image/tiff;image/avif;image/heif;image/heic;image/jxl;
+Keywords=image;viewer;photo;camera;culling;
\ No newline at end of file
diff --git a/data/org.buetow.ggaze.gschema.xml b/data/org.buetow.ggaze.gschema.xml
new file mode 100644
index 0000000..70ddfa4
--- /dev/null
+++ b/data/org.buetow.ggaze.gschema.xml
@@ -0,0 +1,106 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ggaze GSettings schema — org.buetow.ggaze.
+
+  ALL keys are declared up front (M0) with sensible defaults so later modules
+  just read them. See docs/tech-stack.md "Settings keys" for the intended
+  semantics; consumption lands with the matching milestones.
+
+  `window-geometry` is (iiib) = (width, height, fullscreen-as-int-0/1,
+  maximized). The width/height/maximized mapping is finalized in M10; the
+  shape is fixed here so the schema is stable.
+-->
+<schemalist>
+   <enum id="org.buetow.ggaze.sort">
+      <value nick="name" value="0"/>
+      <value nick="capture-time" value="1"/>
+      <value nick="size" value="2"/>
+   </enum>
+
+   <enum id="org.buetow.ggaze.background">
+      <value nick="black" value="0"/>
+      <value nick="dark" value="1"/>
+      <value nick="grey" value="2"/>
+      <value nick="checker" value="3"/>
+   </enum>
+
+   <enum id="org.buetow.ggaze.scroll-behavior">
+      <value nick="zoom" value="0"/>
+      <value nick="pan-when-zoomed" value="1"/>
+      <value nick="navigate" value="2"/>
+   </enum>
+
+   <schema id="org.buetow.ggaze" path="/org/buetow/ggaze/">
+      <key name="sort" enum="org.buetow.ggaze.sort">
+         <default>'name'</default>
+         <summary>Sort order</summary>
+         <description>Sort the folder by name, EXIF capture time, or size.</description>
+      </key>
+
+      <key name="wrap" type="b">
+         <default>true</default>
+         <summary>Wrap at folder ends</summary>
+         <description>Wrap prev/next at the first/last image.</description>
+      </key>
+
+      <key name="background" enum="org.buetow.ggaze.background">
+         <default>'dark'</default>
+         <summary>Viewer background</summary>
+         <description>Background behind the image in large view.</description>
+      </key>
+
+      <key name="scroll-behavior" enum="org.buetow.ggaze.scroll-behavior">
+         <default>'zoom'</default>
+         <summary>Scroll behavior</summary>
+         <description>What the mouse scroll wheel does in large view.</description>
+      </key>
+
+      <key name="slideshow-delay" type="d">
+         <default>3.0</default>
+         <summary>Slideshow delay</summary>
+         <description>Seconds between slides in slideshow mode.</description>
+      </key>
+
+      <key name="thumbnail-size" type="i">
+         <default>128</default>
+         <summary>Grid thumbnail size</summary>
+         <description>Pixel size of grid thumbnails (resizable via +/-).</description>
+      </key>
+
+      <key name="hide-trashed" type="b">
+         <default>false</default>
+         <summary>Hide trashed items</summary>
+         <description>Hide ./Trash/deleted items from the grid entirely.</description>
+      </key>
+
+      <key name="window-geometry" type="(iiib)">
+         <default>(800, 600, 0, false)</default>
+         <summary>Window geometry</summary>
+         <description>(width, height, fullscreen, maximized) restored on launch.</description>
+      </key>
+
+      <key name="destinations" type="a(ss)">
+         <default>[]</default>
+         <summary>Move destinations</summary>
+         <description>Ordered (name, path) pairs for the `m` move popup; order = hotkey order.</description>
+      </key>
+
+      <key name="editors" type="a(ss)">
+         <default>[]</default>
+         <summary>External editors</summary>
+         <description>Ordered (name, command) pairs for the `e` open-in popup; %f = current file.</description>
+      </key>
+
+      <key name="scripts" type="a(ss)">
+         <default>[]</default>
+         <summary>Shell scripts</summary>
+         <description>Ordered (name, command) pairs for the `!` run-script popup; %f/%d expanded, run via /bin/sh -c.</description>
+      </key>
+
+      <key name="enhance-presets" type="a(ss)">
+         <default>[]</default>
+         <summary>Enhance presets</summary>
+         <description>Ordered (name, gegl-graph) pairs for the `a` enhance popup (GEGL only).</description>
+      </key>
+   </schema>
+</schemalist>
\ No newline at end of file