Five decision sites no input reaches: printedGap's blank drop, whitespace row A12, three table declines

What this is

Five decision sites the Sep 7 ablation study (category-collapse.md) could not reach with any input, over 1,876 real documents and the test suite: printedGap's blank-drop arm (src/print/list.ts:838-848; its own test comment says "the recorded gap is already empty here"), whitespace fact row A12 (src/whitespace-fact.ts:429-431, an anchor: reftext holding a multi-space run), and three TableDecline members (unterminated table-layout.ts:288-299, attribute-reference :556-580, and one more the study names) that fire on none of 271 tables and have no test row. Same shape as #260: a branch nothing reaches.

The change

For each: construct a reaching input and pin it, or delete the arm and its census entry (the TableDecline census pins the member set, so a deletion is a census edit). The study's per-site notes are the starting point.

Start with the per-site notes in category-collapse.md, then inspect src/print/list.ts:838-848, src/whitespace-fact.ts:429-431, and the TableDecline members in table-layout.ts:288-299 and :556-580. Determine the missing third TableDecline site from the study and check the related tests and census entry. Done means each site has a pinned reaching input, or its arm and census entry are removed, with the test suite passing.