Infer parallel, perpendicular, equal radius and tangent while drawing

Port of snaporca 2d36d28770. Parity OK: 17 files identical, 8 diverging at their
expected counts.

infer_axis_constraint returned only Horizontal or Vertical. On the
CAD-1000-hours corpus the top two transitions are sketch_dim -> sketch_draw
(5896) and back (5756): the signature of geometry that does not self-constrain
as it is drawn.

Every rule requires the relation to be ALREADY TRUE within tolerance, so nothing
the user drew is moved; parallel/perpendicular and tangent additionally require a
shared endpoint.

TWO LIMITS THE CORPUS RUNG FORCED, neither visible to the unit tests:

1. At most ONE constraint per rule per new entity, not one per PAIR, and no
   one-at-a-time fallback for the relations batch. EqualRadius has no locality
   restriction, so 200 equal holes produced ~20000 candidates; the rejected batch
   then cost a solve per constraint and pinned the app at 95% of a core with the
   MCP socket unresponsive.

2. Relations only for gesture-sized batches. "A scripted add is not a drawn
   gesture" is already this file's rule at its bulk call site (snaporca-8xg1), and
   EqualRadius also couples geometrically distant entities, merging independent
   connected components and defeating the partitioning that makes large sketches
   solvable (snaporca-yww4). With the cap alone geometry stayed correct (32/32
   sheets clean) but seven of the largest timed out, including MPD681 -- the sheet
   that call site's own comment names.

Also fixes the tolerance leak behind 2: the bulk path asks for exact inference
with ang_tol_rad = 0 but len_tol_frac kept its 0.01 default.

ALSO independent of this feature: run-kernel-tests.sh defaulted to
TAGS=[CadDocument] while four CAD test files carry their own tags and nothing
selected them (2624 assertions / 206 cases reported, 7648 / 264 actual). All 58
dark cases were passing; the coverage was never exercised.

VERIFICATION LIMIT, as with the previous three commits: this fork's kernel suite
still cannot run (find_package(assimp) at configure time, snaporca-w80c). Shared
sources are byte-identical to snaporca's, where kernel is 7651 assertions / 265
cases and ALL LADDERS HELD 7/7.

scripts/CAD/run-kernel-tests.sh

@@ -36,7 +36,17 @@ VOL="${BUILD_VOL:-orcacad_kerneltest}"
 # circle-line tangency is fixed (snaporca-tkz), and the internal-thread case turned out to have
 # correct geometry and a wrong reference in the test (snaporca-kzy). A green run here now means
 # the whole CAD suite passed, not "everything except the two we gave up on".
-TAGS="${TAGS:-[CadDocument]}"
+#
+# ...and that claim was still not true, because the default tag was [CadDocument] alone while
+# four CAD test files carry their own tags and NOTHING ELSE selected them. test_sketchinference
+# ([inference], 15), test_sketchedit ([SketchEdit], 23), test_sketchconstraints
+# ([SketchConstraints], 8) and test_sketchimport ([SketchImport], 4) never ran here, nor did the
+# older [slvs]-only cases in test_slvs_constraints. Measured 2026-08-31: the default reported
+# 2624 assertions / 206 cases, the full set 7648 / 264 -- so the gate was speaking for about a
+# third of the assertions, and a whole file could be added, tagged by its own convention, and
+# stay dark while the suite printed green. All 58 were passing; the coverage was simply never
+# exercised. Adding a tag here is now part of adding a test file.
+TAGS="${TAGS:-[CadDocument],[inference],[SketchEdit],[SketchConstraints],[SketchImport],[slvs]}"
 HOST=""
 
 while [[ $# -gt 0 ]]; do