[bug] conformance-check.sh reports "0 measurable rows" on a per-BRD coverage-ledger layout #260

What broke:
project-bin/conformance-check.sh --module <M> reads architecture/modules/<M>/coverage-ledger.md. In a per-BRD layout that file is only an index; the rows live in coverage-ledger/F00N-*.md. Master 2fcdf5e still has no coverage-ledger/ lookup.

Command / script run (exact invocation):
bash bin/conformance-check.sh --module ModuleA

Expected vs. actual:
Expected: rows from every per-BRD ledger measured.
Actual, exit 2:

FAULT: 0 measurable rows extracted from 1 ledger(s).

Field evidence:
A consuming project (Mendix 11.14.0, macOS, toolkit 2fcdf5e, mxcli v0.24.0), 2026-10-10, four modules. One module has no ledger of its own; its rows sit in another module's per-BRD ledger.
Workaround that works:
LEDGER_FILE=architecture/modules/ModuleA/coverage-ledger/F002-<slug>.md bash bin/conformance-check.sh --module ModuleA
gave 128 rows, 66 measured, 66 OK, 0 STALE, 0 UNDERSTATED.

Proposed fix (hypothesis):
When <M>/coverage-ledger/ exists, measure every *.md in it, one report per BRD (report-<date>-<BRD>.tsv) so runs do not overwrite each other. Document LEDGER_FILE in the usage line. A ledger with no table should say "this is an index, rows are in ..." instead of "0 measurable rows".

Golden input: the FAULT line above, verbatim.