build: bun run build fails on @cap/sdk-recorder DTS — package is outside the typecheck graph #2915

Symptom

bun run build exits 1 on @cap/sdk-recorder:

@cap/sdk-recorder:build: src/index.ts(88,38): error TS2345: Argument of type 'EventHandler<K>' is not assignable to parameter of type 'EventHandler<keyof RecorderEventMap>'.
@cap/sdk-recorder:build:   Type 'keyof RecorderEventMap' is not assignable to type 'K'.
@cap/sdk-recorder:build:     'keyof RecorderEventMap' is assignable to the constraint of type 'K', but 'K' could be instantiated with a different subtype of constraint 'keyof RecorderEventMap'.
@cap/sdk-recorder:build: Error: error occurred in dts build
@cap/sdk-recorder:build: error: script "build" exited with code 1

Reproduces standalone with bun run --cwd packages/sdk-recorder build (exit 1). It is pre-existing: it reproduces with the Bun 1.4.4 branch changes stashed at c3f0a92.

Root cause

packages/sdk-recorder/src/index.ts:48

private listeners = new Map<string, Set<EventHandler<keyof RecorderEventMap>>>();

on<K extends keyof RecorderEventMap>(event: K, handler: EventHandler<K>) erases the key type with an explicit cast on add (line 86) but not on delete (line 88):

if (set) set.add(handler as EventHandler<keyof RecorderEventMap>);
return () => {
	this.listeners.get(event)?.delete(handler);
};

Why CI does not catch it

• packages/sdk-recorder is not in the root tsconfig.json references (ui, recorder-core, ui-solid, utils, desktop, chrome-extension, web), so bun run typecheck never checks this package.
• No workflow runs bun run build (grep "bun run build" .github/workflows/*.yml returns nothing).

Both the TypeScript 5.9.3 checker used by tsup's DTS build and Bun's TypeScript 7.1-dev checker (bun check -p packages/sdk-recorder) report the same error, so this is not a checker-version artifact.

Proposed fix

Cast at delete as already done at add:

this.listeners.get(event)?.delete(handler as EventHandler<keyof RecorderEventMap>);

Beyond the one-line fix, add the package to the root tsconfig.json references so bun run typecheck covers it. A CI job that runs bun run build (or at least turbo run build --filter=@cap/sdk-recorder) would keep this from regressing.

Note: the SIGSEGV/SIGBUS seen when running the full build is unrelated and environmental — it reproduces under Node 26 as well, and the build is stable at --concurrency=2.