The limits read `wall_segments`, so a document older than the catalogue
reports no walls at all — and therefore no violations, whatever its geometry.
Comparing that raw baseline against a candidate the card had already migrated
counted every inherited violation as new, and a legacy plan could not take an
unrelated edit at all: renaming a room was refused with junction_limit_angle.
Spec §3 forbids exactly this, and the frontend had already learned the same
lesson in 4758767e; the backend mirror simply never got the second half.
validate_junction_limits now runs both documents through
commit_wall_segment_model before counting. A document that cannot be migrated
is not this validator's verdict — the wall-model barrier owns that error and
reports it with its own code — so it degrades to "no baseline to inherit".
The regression is pinned twice: a test that asserts the legacy baseline reads
clean raw and carries the apex once migrated, and the mutant
junction-limit-backend-raw-baseline. Both fixtures that exercise the barrier
were rebuilt as real documents (rooms plus walls), because the previous ones
put walls in wall_segments with no rooms and did not survive migration.
Issue: #329
User-Visible: no
custom_components/houseplan/junction_limits.py repeats П1-П4 for the write
barrier in websocket_api, counting per rule so an inherited violation still
round-trips, and raises JunctionLimitError with the stable code
junction_limit_<rule>.
П5 is deliberately not mirrored — it judges the rendered wall bodies, and a
second mitre/inset pipeline in Python would drift more dangerously than the
rule it guards. Optimize stays outside the check for the same reason migration
and import do: it repairs existing geometry.
test_parity_with_the_frontend_checks feeds identical fixtures to the TS
functions and to this module and demands the same verdict, so the two
implementations cannot silently diverge.
Issue: #329
User-Visible: no
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