A button create-from takes sourceStatusOnRetire too

[nedelcho-delchev-tues]

Fixes #7647

sourceStatusOnRetire: was refused on a create-from with no event:. The reasoning was that a button carries no at-most-once guard, so nothing blocks a replacement and the button already reissues — an authored key that would generate nothing.

That holds only without a completion hook. With sourceStatus: declared, the hook flips the source off the status the button is offered from, and the implied fromStatus deny of exactly that status (#7068) answers the second click with a 409. The proforma stays INVOICED, immutableWhen locks it, and nothing in the model can move it back. The hook blocks the button exactly as the guard blocks the trigger, and the declared inverse is the same move back in both shapes.

What changed

• The parser refusal is deleted. A reopen with no sourceStatus is still refused, there being nothing to invert, and so is every other combination that could never fire (the same status twice, mode: append, a cross-model target, a target with no lifecycle, an unclassified nomenclature).
• putSupersededTarget no longer returns early for a button shape. It emits the reopen half and leaves hasRetiredStatus false: the stage-aware step-over belongs to an at-most-once guard this shape does not have, so there is nothing for it to step over.
• Its unclassified-nomenclature warning now names which of the two is at stake, since the sentence about a guard reads as noise on a shape that has none.

Covered by GeneratesIntentTest.acceptsAReopenOnAButtonCreateFromWithACompletionHook (and its sibling, which pins the refusal that stays) and GlueGeneratesTest.aButtonCreateFromEmitsTheReopenWithoutTheStageAwareGuard. The engine-intent suite is green: 1481 tests.