Update ImageShowTool render message and WebSearchTool image handling

fix(ImageShowTool): use terminal height instead of width for dimension calculation

feat(ImageShowTool): use timg for full-res Kitty image, dedup placement

feat: render image directly to terminal fd, keep empty placeholder for TUI layout

fix: use env-var terminal detection to avoid stdin conflicts in TUI

refactor: move ink-picture rendering from call() to UI React tree

feat: register ImageShowTool as a proper buildTool with prompt + UI

refactor: extract UI from ImageShowTool into separate component

refactor: rewrite ImageShowTool with new architecture