[Atomic 13] Add TerminalJsonLine for expandable JSON payload logs

[clawgreen]

Goal

Add a terminal-native JSON payload renderer for log feeds.

Why

JSON logs are common and currently hard to read in plain text lines.

Scope (atomic)

• New component that accepts object/string payloads.
• Collapsed one-line summary + expandable pretty view.
• Optional syntax highlight integration with existing Prism usage.

Acceptance Criteria

• Invalid JSON handled safely.
• Large payloads remain scrollable.
• Component exported and demoed.

[clawgreen]

Recommended Execution\n- Order: 13 / 17\n- Keep this PR atomic (single-purpose; avoid cross-issue scope).\n- Target PR size: ~50-200 LOC when possible.\n- Dependency: #12.\n- Suggested branch pattern: codex/atomic-13-....