Fix tus upload rejection handling

[kvz]

Why

API2 PagerDuty incident Q33YSSJS2BXHOF exposed that a transient tus create-upload failure can reject the caller-facing startPromise and also leave the SDK's internal upload URL/completion bookkeeping promises rejected without handlers. In API2 that second, duplicate rejection reached the process-wide unhandledRejection handler after the original createAssembly() failure had already been caught and reported.

Changes

• Attach handlers to tus upload bookkeeping promises when they are created, so the caller still receives the primary upload failure while duplicate internal rejections do not become unhandled.
• Add a regression test that fails before the fix by observing two unhandled rejections after a simulated tus onError.
• Add patch changesets for @transloadit/node, @transloadit/mcp-server, and transloadit per release-coupling policy.

Tests

• yarn workspace @transloadit/node test:unit --run ./test/unit/tus.test.ts
• yarn check

Related API2 pager PR: https://github.com/transloadit/api2/pull/8307