feat(tui): add vi basic mode extension for prompt and editor

[ryanwyler]

Summary

A modular vi mode implementation for the OpenCode TUI prompt with support for standalone editors.

Provides the vi extension for prompt but also for the Project Files Viewer and Editor https://github.com/anomalyco/opencode/pull/7017

Core Features

• Normal/insert modes with standard vi keybindings
• Movement: h/j/k/l, w/b/e, 0/$, G, {/}, %, g{n}g, ctrl+f/b
• Delete: x, {n}x, dd, d{n}d, dw, d{n}w, D, d$, dG, d{n}G
• Change: cc, c{n}c, cw, c{n}w, C, s
• Yank: yy, y{n}y, y$, yG, y%, y{, y}
• Paste: p/P (line-wise or character-wise)
• Multiline: o, O, J
• Other: r, ~, ., u, ctrl+r
• Search: /, ?, n, N (with regex support)
• Search operators: d/, d?, c/, c?, y/, y?

Configuration

• prompt_vi_basic KV setting to enable/disable
• vi_basic_clip_x KV setting for clipboard behavior
• Toggle via command menu

Architecture

• PromptExtension interface for modular prompt extensions
• lineNumbers option for gutter redraw (opentui workaround)
• Two modes: full (for standalone editors) and prompt (for prompt input)

Files Changed

File	Changes
lib/vi-basic-core.ts	Core vi mode logic
lib/vi-basic-extension.tsx	Prompt extension wrapper
lib/prompt-extension.ts	Extension interface
component/prompt/index.tsx	Integration