Show the photograph the way it was taken

Nothing read EXIF orientation, so every frame from a body held sideways
lay on its side — in the grid, in develop, and in the read-only preview.

The tag is honoured as part of *reading the file*, at the same standing
as a RAW's masked-photosite crop, never as an edit. It lives as a
baseline on Framing rather than as a starting value for quarter_turns,
which is what keeps four things true: a sideways file opens unmodified,
reset returns it to upright rather than to the sensor's scan order, its
sidecar stays empty, and the rotate button still moves the image 90°
whatever the file underneath it says.

Framing::effective composes the baseline with the user's own turns
through the group law rather than by adding turns and OR-ing flags. The
naive version gets one case wrong — an odd baseline turn plus a user
mirror — and gets it wrong quietly, because the result is still a
plausible orientation. The composition collapses to a single
permutation, so obeying the tag costs nothing per pixel.

dr_decode::orientation is a header-only IFD walk, separate from
metadata() for the reason the entry points are separate at all: the grid
asks once per cell and must not build a rawler decoder to get one tag.
CR3 and RAF fall back to the full read, being neither TIFF nor JPEG.

Written down as FR-DEV-3h.

Known gap: thumbnails cached before this stay sideways. The store is
keyed by file and size, and its shards sync — invalidating them would
have every client re-download 25 MB a shard, which is not this commit's
call to make.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

core/dr-pipeline/src/graph.rs

@@ -268,6 +268,15 @@ impl EditGraph {
         self.framing.rotate_quarters(turns);
     }
 
+    /// Record how the file stored its pixels, from its EXIF orientation.
+    ///
+    /// Set when the image is opened and never by an edit — see
+    /// [`crate::framing::Framing::set_baseline`]. Survives [`Self::reset`],
+    /// so it is safe to call before restoring a sidecar.
+    pub fn set_orientation(&mut self, orientation: dr_types::Orientation) {
+        self.framing.set_baseline(orientation);
+    }
+
     /// Whether any operation, or the framing, currently changes the image.
     ///
     /// Asks the framing whether it *edits*, not whether it is active: zoom