fix(tui): externalize koffi from bun binary builds

Changed koffi import from top-level to dynamic require in
enableWindowsVTInput() and added --external koffi to bun build.
This prevents embedding all 18 platform .node files (~74MB) into
every compiled binary. For Windows builds, only the win32_x64
koffi.node is shipped alongside the binary.

Binary size reduction: darwin-arm64 142MB -> 67MB, archive 43MB -> 28MB.

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Externalized koffi from bun binary builds, reducing archive sizes by ~15MB per platform (e.g. darwin-arm64: 43MB -> 28MB). Koffi's Windows-only `.node` file is now shipped alongside the Windows binary only.
+
 ## [0.54.0] - 2026-02-19
 
 ### Added

packages/tui/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Changed koffi import from top-level to dynamic require in `enableWindowsVTInput()` to prevent bun from embedding all 18 platform `.node` files (~74MB) into every compiled binary. Koffi is only needed on Windows.
+
 ## [0.54.0] - 2026-02-19
 
 ## [0.53.1] - 2026-02-19

packages/tui/src/terminal.ts

@@ -1,5 +1,4 @@
 import * as fs from "node:fs";
-import koffi from "koffi";
 import { setKittyProtocolActive } from "./keys.js";
 import { StdinBuffer } from "./stdin-buffer.js";
 
@@ -174,6 +173,10 @@ export class ProcessTerminal implements Terminal {
 	private enableWindowsVTInput(): void {
 		if (process.platform !== "win32") return;
 		try {
+			// Dynamic require to avoid bundling koffi's 74MB of cross-platform
+			// native binaries into every compiled binary. Koffi is only needed
+			// on Windows for VT input support.
+			const koffi = require("koffi");
 			const k32 = koffi.load("kernel32.dll");
 			const GetStdHandle = k32.func("void* __stdcall GetStdHandle(int)");
 			const GetConsoleMode = k32.func("bool __stdcall GetConsoleMode(void*, _Out_ uint32_t*)");