P5-T6. Adds docs/MATCHING_COOKBOOK.md (nine byte-proven compiler/assembler
findings, each with basis and limit), docs/MATCHING_CONVENTIONS.md (what counts
as a match, registry format, source naming, duplicate sharing, symbols, the
verification procedure, the firewall) and docs/PHASE5_VERIFICATION.md (outcome,
clean gates, bounded negatives, milestone request).
Tooling: make test and make check targets; region objects are now
symbol-localized so the documented duplicate-sharing mechanism (N registry rows
-> 1 source) links, covered by a synthetic test (53 tests).
Clean gates: 53/53 tests; make clean/all/cmp/SHA-1 green; make gate with one C
region -> c_regions=1, 0 differing bytes, SHA-1 e173426c...; 57 tracked files, 0
under any prohibited root. Phase 5 is not closed until the milestone is
confirmed.
Christopher Williams
defbf446eb