fix(args-builder): hydrate Custom JSON, CEP install default, UI polish

[Interchouette]

Summary

• CEP tab with no entrypoint shows install schema (no more empty CEP-78).
• Custom tab: at least one row; prefers Args JSON for custom WASM; flush textarea before opening the builder.
• Custom tab moved to the right; column scrollbars removed; Transaction card bottom margin restored.

Test plan

• Open Args builder on CEP-78 with no entrypoint: install fields appear
• Custom with empty Args JSON: one blank row
• Paste Args JSON, click build: rows and nested types prefill
• No column scrollbars; Transaction card shows bottom margin
• cd www && npx nx test deployer

Made with Cursor