[johnnyt]

Bead: srb-1kv

What changes

The conformance runner (under test/conformance/, none of it ships) now completes the statifier suite:

• The diff pair is driven, not compared. A host object's to_source, expect_diff, mapping and expect_compatible_at are accepted (UNCOMPARED_HOST_KEYS in Conformance::Drive) and compared by nothing, so a diff case is driven like any host case and agrees on its configurations and its sends. This follows the reference's harness at v2.16.0, whose moduledoc in lib/mix/statifier/corpus/host_case.ex says "this runner compares none of them". Any other unknown host key is still refused by name.
• expect_position is compared. Once a step's configuration agrees, Conformance::PositionExpectation.at_step renders the state's position from Statifier.export_position as the reference's PositionExpectation.render/1 renders its export (lib/mix/statifier/corpus/position_expectation.ex at v2.16.0) and compares it as a JSON value:
  • configuration, entered_states, states_to_invoke: sorted id arrays;
  • history_values: each history id to its sorted recorded ids;
  • active_invocations: {state, index} per live invocation, sorted by state then index, the invoke id left out;
  • running: as exported;
  • datamodel: the position's tagged texts decoded, without _event, _ioprocessors and _sessionid, and without _name unless the <scxml> element carries a name attribute (the reference's drop_unset_name/2); the undefined value as null; a date, datetime or duration (or a list or map holding one) fails the step naming the variable.
  • A differing member is named with both values as JSON, "nothing" for an absent one, in the reference's wording.
• A document with an unnamed state fails a case that states a position before the case is driven (the reference's named/1, counting every state but the root).
• Step data. A step of a case stating a position sends its event's data, as the reference's harness does for every case it runs through run/2; before this, only a case with a host object did. No corpus case exercises the hostless form today; a test pins it.
• The ratchet records the new passes (the ten diff cases and the four position cases): the statifier claim now holds every case of its suite, and the registry check passes over the whole run.
• conformance/README.md says what the runner does with the diff pair and with expect_position, and drops the stale sentence that called the accepts keys unhonoured; README.md's claim table and its "not claimed yet" list follow the registry.

No lib/ change and no changelog fragment (a runner-only change, per changelog.d/README.md).

Evidence

• Full gate (mise exec -- bundle exec rake) green on the committed tree: rubocop clean over 199 files; corpus:check agrees at v2.16.0; registry: 309 entries pass today, statifier: 0 of 36 cases not yet claimed; 622 runs, 0 failures; line coverage 99.81%, branch 96.46%.
• New tests: test/conformance/position_expectation_test.rb (the rendering, the invocation shape, the _name rule, the date/datetime/duration refusal, the member-by-member reason, hostless step data, the unnamed-state refusal, the diff pair driven and uncompared). statifier_suite_test.rb now requires every case of the suite to pass and a case with one flipped position member to fail naming it.
• Sabotage: each new test carries its mutation in a comment above it; every mutation of this change's own lines turned its named test red on an assertion, and each file was restored byte-equal before the next.