build: bundle all non-native runtime deps into dist/cli.js

The previous build.mjs externalized 11 packages at bundle time, which
forced every downstream consumer to provide them at runtime via an
ancestor node_modules/. That worked for `npm i -g kanban` and monorepo
dev, but the Electron packaging context ships dist/ to a location with
no ancestor node_modules/, so the externals couldn't resolve there.

Drop the externals list to just `node-pty` (the only genuinely
non-bundlable package — it's a native addon with a compiled binding
and a spawn-helper binary on disk). esbuild inlines the other 10:

  @sentry/node, proper-lockfile, tree-kill, ws, open, @trpc/client,
  @trpc/server, @modelcontextprotocol/sdk, commander, zod.

Result: dist/cli.js is a single self-contained 16MB bundle with one
runtime-resolved external (node-pty). In the Electron packaging PR
downstream, node-pty gets rebuilt for Electron's ABI by
electron-builder's install-app-deps into
Resources/app.asar.unpacked/node_modules/, and cli.js resolves it via
standard ESM walk-up from its own location inside app.asar.unpacked/.

No dist/node_modules/ staging, no build-time `npm install`, no
duplicate node-pty, no version drift between what esbuild saw and
what the runtime resolves.

scripts/build.mjs drops from ~190 lines (including the staging code
the reviewer flagged as unusual) to ~60 lines of pure esbuild config.

Author: johnwschoi

scripts/build.mjs

@@ -1,19 +1,11 @@
 import * as esbuild from "esbuild";
 
-/** Modules that must stay external (native addons, large runtime deps). */
-const external = [
-	"node-pty",
-	"@sentry/node",
-	"proper-lockfile",
-	"tree-kill",
-	"ws",
-	"open",
-	"@trpc/client",
-	"@trpc/server",
-	"@modelcontextprotocol/sdk",
-	"commander",
-	"zod",
-];
+/**
+ * Runtime externals. `node-pty` is a native addon with a compiled binding
+ * and a spawn-helper binary that must live on disk, so it can't be bundled.
+ * Everything else esbuild can inline.
+ */
+const external = ["node-pty"];
 
 /** Bake OTEL telemetry env vars into the bundle at build time. */
 const define = {