rugnux: the mounting's cost is computed exactly from the measured group, not guessed from an angle

Offline, a merged rotation run has what a still lacks - a determined point group and an exact
indexed orientation - so the run-level number no longer needs the pessimistic presumed-diad
bound, and it no longer uses the nearest-axis angle either. That 15-deg warning heuristic was
wrong in both directions: an aligned in-plane 2-fold of a dihedral group is repaired by the
principal axis, a cubic group is never severe in any orientation, and a lone diad perpendicular
to the spindle is severe with no axis anywhere near the spindle at all.

The group's proper rotations are applied to the sweep's blind double cone in the crystal's
actual orientation, and what no operator maps onto measured territory is counted, weighted by
each shell's own cone width so the result is a fraction of unique reflections to this run's
resolution limit. Friedel and the improper operators need no separate handling - the cone and
the measured region are both inversion-symmetric. The number is machine-readable on purpose:
SPINDLE_LOST_UNIQUE_FRACTION in the report (0-1, a bare number a pipeline can act on) and
/entry/MX/spindleLostUniqueFraction in the master, with the warning prose only on top of it,
fired when the group recovers less than half the cone's content. REPORT_VERSION stays 7: the
format's own rule is that adding a key does not move it.

This also settles what the nearest-axis keys hedged: with the measured group the mounting is
cleared or convicted exactly, so their documentation now calls them descriptive and points at
the new key for the verdict. Verified against Monte Carlo: P1 loses 2.0% of unique reflections
at theta_max = 15 deg with nothing repaired; a lone diad on or perpendicular to the spindle
repairs nothing; an axis of order >= 3 perpendicular to the spindle repairs everything; 622
with an in-plane diad on the spindle loses nothing; cubic loses nothing in any orientation.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EFEJG6WBQv8th4UJFNe53N

frame_serialize/CBORStream2Serializer.cpp

@@ -802,6 +802,7 @@ void CBORStream2Serializer::SerializeSequenceEnd(const EndMessage& message) {
     CBOR_ENC(mapEncoder, "indexing_rate", message.indexing_rate);
     CBOR_ENC(mapEncoder, "bkg_estimate", message.bkg_estimate);
     CBOR_ENC(mapEncoder, "spindle_blind_fraction", message.spindle_blind_fraction);
+    CBOR_ENC(mapEncoder, "spindle_lost_unique_fraction", message.spindle_lost_unique_fraction);
 
     CBOR_ENC(mapEncoder, "rotation_lattice_type", message.rotation_lattice_type);
     if (message.rotation_lattice.has_value())