Reviewer addition to the round-trip stability matrix: besides "attr absent" and
"attr has a real value", a string attr in the empty-string class has a third,
degenerate state — a LITERAL "" (a user types alt/title/name in the editor then
deletes it, and Tiptap persists `attr: ""`, distinct from never-set). The fix's
`getAttribute(...) || null` coercion normalizes such a stored "" to the default
on the FIRST round-trip (a one-time "" -> null diff) and is byte-stable from the
SECOND round-trip on.
Adds a convergence contract to the reusable matrix helper (emptyStringClass flag
+ runConvergenceCase): pass 1 must converge the attr to its schema default (NOT
asserted byte-stable vs the "" input — that is the intended one-time
normalization); pass 2 must deep-equal pass 1 (idempotent thereafter). Driven for
every empty-string-class attr across image + the media family (image/drawio
alt+title, video alt via aria-label, pdf/attachment name, attachment mime).
Documents the one-time normalization so a future sync/QA diff does not flag the
single "" -> null change as converter corruption.
Gate: package suite 33 files / 682 tests passed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
agent_coder
c192f2a2e1