Enforce the style data producer/consumer lockstep structurally

[kmcginnes]

Description

The ADR from #2112 records this as a Consequence:

Producer and consumer must stay in lockstep. A new per-type style property must be added in two places together — the ge_* field + its producer, and the matching data(…) mapper. Editing one side alone silently drops the style.

Nothing enforced it, and the migration had already dropped assertions for ge_labelBackgroundOpacity, ge_labelBackgroundColor, ge_labelBorderWidth, ge_labelBorderColor, ge_labelBorderStyle and the arrow-colour / distance mappings — asserted nowhere.

This closes the loop by comparing key sets rather than listing field names, so it cannot rot the way a hand-written list does. Both directions:

• every ge_* key the producers emit appears as a data(...) mapper somewhere in the stylesheet
• every ge_* mapper corresponds to a key a producer emits

Non-ge_* mappers (displayName) come from the rendered entity rather than these producers, so they're excluded by prefix, not by name. It walks every rule rather than hardcoding node / edge, so a legitimately re-added gated selector is still covered.

Verified by deliberate probe: adding a bogus mapper and a bogus producer field each failed the expected direction, then both probes were reverted.

How to read

One new describe block at the end of useGraphStyles.test.tsx.

[kmcginnes]

Superseded by #2128, which consolidates this stack into a single PR targeting #2112. Same commits, same end state — the branch there is byte-identical to the tree these were cut from, rebased onto schema-view-style-perf after #2118 was squash-merged into it.