chore: remove unused workflows and stale CI config (#1662)

* chore: remove unused Asana and Claude workflows

no longer used

* chore: remove unused issue response-time workflow

The workflow stamped response_time_in_business_days into a hidden
probot metadata block on each issue. No consumer reads the value.

* chore: remove stale Travis config and superseded root files

- .travis.yml: pins Xcode 11.1 / iOS 13.1 from 2019; CI runs on
  .github/workflows/ci.yml (Xcode 16.4).
- issue_template.md: shadowed by .github/ISSUE_TEMPLATE/*.yml form
  templates, which GitHub prefers.
- default: ci.yml writes this file every run, so the committed copy
  is not load-bearing.

Author: nan-li