Graph evidence 5/8: card section — contract check (missing-implementations) #12

Part of the graph-evidence integration.

What

For each member-added trigger (a method added to an interface/base class in the diff), run prism missing-implementations 'Type.method' on the head index.

Card section:

### Contract check
⚠ Renderer.flush added — 2 implementors do not implement it:
    render/SVGRenderer.java (compile error when required)
    render/PDFRenderer.java
✔ (or) all 14 implementors provide it

Rules

• Relay the engine's buckets as-is: missing (compile errors), abstractMissing (informational), unverifiable (extends chain leaves the index — render as "verify manually", never as broken).
• defaultProvided: true renders the engine's own note: nothing is broken today; the list is who breaks if the member becomes required.
• Same completeness-field discipline as Graph evidence 3/8: card section — change-set completeness (change-impact) #10.

Acceptance

• shale-test-bed PR adding an interface member with one missing implementor → ⚠ naming exactly that type; adding the implementation in the same PR flips it to ✔.
• Runs in seconds, before CI's compiler would report the same thing minutes later — the card cites the time saved.