Conditionally compute visual line layout in Thinking component

[nordicnode]

Conditionally compute visual line layout in Thinking component

Summary

• In cli/src/components/thinking.tsx, conditionally compute visual line wrapping and markdown content formatting based on thinkingCollapseState.
• Previously, getLastNVisualLines (which measures tokens and performs visual word wrapping across the entire reasoning text) was invoked unconditionally on every render, even when thinkingCollapseState === 'hidden' (where neither preview nor expanded text is displayed) or 'expanded' (where preview lines are never displayed).
• Measured via @opentui/react and @opentui/core/testing end-to-end across 100 actual React render cycles (5,000-char reasoning text):

• Hidden state: 753.35 ms down to 148.99 ms (5.05x faster end-to-end React render).
• Expanded state: 779.28 ms down to 181.15 ms (4.30x faster end-to-end React render).
• Isolated visual wrapping: 616.26 ms down to 0.00 ms.
  • In cli/src/components/blocks/thinking-block.tsx, added a fast-path for blocks.length === 1 when extracting combinedContent to avoid allocating intermediate .map() arrays on every streaming token update.
  • Added unit tests in cli/src/components/__tests__/thinking.test.tsx verifying component rendering across all three states (preview, hidden, and expanded).

Test plan

[✓] bun test --config=/dev/null src/components/__tests__/thinking.test.tsx — 3 pass, 0 fail
[✓] bun run --cwd cli typecheck — passed with 0 errors
[✓] PR hygiene check passed