Fills 3 common UI gaps the 47-tool set didn't cover:
- add_image_placeholder_v0: gray box + centered icon + optional
caption. The "future image slot" affordance. Separate from G()
(which fetches real images). Emits frame+fill, NEVER image node
(empty image renders as broken indicator).
- add_comment_v0: avatar + (author + timestamp) header + body.
Social / UGC / feedback unit. Does NOT handle replies / likes /
action menu — compose via batch_design.
- add_modal_shell_v0: dimmed scrim + centered card (rounded,
shadowed) + title + optional subtitle. "Shell" in the name is
deliberate — this is chrome only; body content goes into the
`modal-shell-card` role via a follow-up insert.
Wired across all three paths (pen-core buildX + pen-mcp handler +
routes + schema + apps/web shim + Nitro SERVER_BUILDERS) + elements.md
decision-tree entries + keyword map + examples + 3 pen-mcp handler
tests (22 cases total) + 3 A/B v1 corpus prompts in ab-v1/ +
parametric builder test CASES auto-extended in 9 files.
Milestones:
- Tool count: 47 → 50
- Test count: 3045 → 3114 (+69)
- A/B v1 corpus: 5 → 8 prompts
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