fix(ink): sync native cursor for CJK IME and optimize frame rendering

[HUQIANTAO]

Problem

CJK IME candidate popups appeared at wrong position (top-left) because the native terminal cursor was not synced to the visual input position. The custom ▌ cursor character also animated left-to-right during IME composition because each keystroke triggered a separate re-render.

Solution

Cursor sync

• Export useDeclaredCursor hook from Ink and use it in PromptInput to park the native cursor at the visual input position — fixes IME popup alignment
• Skip redundant cursor declaration updates when position is unchanged (prevents jitter during IME preedit commit)
• Use native terminal cursor instead of custom ▌ character

Frame rendering optimization

• Merge cursorMove + stdout patches and consecutive stdout patches in the optimizer — reduces per-cell rendering
• Always send BSU/ESU in inline mode for atomic frame rendering
• Batch rapid input (IME pinyin + committed CJK) via setTimeout(0) so multiple keystrokes coalesce into a single re-render — the cursor jumps directly to the final position

Files changed

• packages/ink/src/components/App.tsx — stop hiding native cursor
• packages/ink/src/hooks/use-declared-cursor.ts — add position-comparison guard
• packages/ink/src/index.ts — export useDeclaredCursor
• packages/ink/src/ink.tsx — always send BSU/ESU in inline mode
• packages/ink/src/optimizer.ts — merge consecutive stdout patches
• packages/ink/src/terminal.ts — import cursorPosition
• src/cli/ui/PromptInput.tsx — cursor sync + input batching