Add Export Fused ROI CSV export

Lets a user export the current ROI as one CSV with a column per selected
angle's value (RF peak freq, Bias A, Bias B, or velocity), once angles share
a common (x, y) grid -- either via a live Fusion alignment result or because
the open file is itself a previous Alignment Wizard export whose angles
already share one grid on disk. Never triggers a background compute; angles
without cached/stored data for the chosen value type are simply unavailable
in the picker.

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

tests/test_fused_export.py

@@ -0,0 +1,75 @@
+"""SrasFile.angles_share_raw_grid(): the no-alignment-needed gating path for
+Export Fused ROI.
+
+A plain multi-angle scan gives each angle its own bounding box and stage
+x_start (scan_format.md's whole reason v6 geometry is per-angle), so it must
+read as "not shareable" without a live alignment. A file the viewer's own
+Alignment Wizard exported repeats one Per-Angle Geometry record and one Row
+Table span for every angle (scan_format.md, "Files written by the viewer's
+Alignment Wizard"), so it must read as "shareable" with no alignment needed
+at all.
+
+No Qt: this exercises sras_format/sras_compute/sras_align_export directly,
+mirroring tests/test_align_export.py.
+"""
+
+import sras_align_export as export
+import sras_compute as compute
+from sras_format import SrasFile
+import tools.make_test_sras as gen
+
+_THRESHOLD_MV = 80.0
+
+
+def test_single_angle_file_always_shares_its_grid(tmp_path):
+    path = tmp_path / "one_angle.sras"
+    gen.write(path, n_angles=1)
+    sras = SrasFile(str(path))
+    assert sras.angles_share_raw_grid()
+
+
+def test_plain_multi_angle_file_does_not_share_its_grid(tmp_path):
+    """tools.make_test_sras.write gives every angle its own geometry and
+    stage x_start (build()'s `x_start = -0.5 + 0.1 * a`), matching how real
+    v6 scans vary per angle — so this must read as "not shareable"."""
+    path = tmp_path / "plain.sras"
+    gen.write(path, n_angles=3)
+    sras = SrasFile(str(path))
+    assert not sras.angles_share_raw_grid()
+
+
+def test_wizard_exported_file_shares_its_grid(tmp_path):
+    src_path = tmp_path / "rotating.sras"
+    meta = gen.write_rotating(src_path, n_angles=4)
+    sras = SrasFile(str(src_path))
+    params = {a: compute.ManualAngleParams(rot, shift)
+              for a, (rot, shift) in meta["truth"].items()}
+    result = compute.build_manual_alignment(sras, 0, _THRESHOLD_MV, params)
+
+    out_path = tmp_path / "rotating_aligned.sras"
+    export.write_aligned_sras(sras, result, out_path)
+    out = SrasFile(str(out_path))
+
+    assert not sras.angles_share_raw_grid(), (
+        "sanity check: the *source* rotating scan must NOT already share a "
+        "grid, or this test would not actually exercise the wizard export")
+    assert out.angles_share_raw_grid()
+
+
+def test_mutated_angle_breaks_the_shared_grid(tmp_path):
+    """A loaded SrasFile's x_start_mm is a public per-angle array (as
+    tests/test_gui.py::test_alignment_geometry_is_stage_independent also
+    relies on) -- mutating one angle's start must be visible here too."""
+    src_path = tmp_path / "rotating.sras"
+    meta = gen.write_rotating(src_path, n_angles=3)
+    sras = SrasFile(str(src_path))
+    params = {a: compute.ManualAngleParams(rot, shift)
+              for a, (rot, shift) in meta["truth"].items()}
+    result = compute.build_manual_alignment(sras, 0, _THRESHOLD_MV, params)
+    out_path = tmp_path / "rotating_aligned.sras"
+    export.write_aligned_sras(sras, result, out_path)
+    out = SrasFile(str(out_path))
+    assert out.angles_share_raw_grid()
+
+    out.x_start_mm[1] += 1.0
+    assert not out.angles_share_raw_grid()