Polish README FAQ copy for leaf-node auth callout behavior

[Copilot]

This updates the README FAQ added in PR #27 to address all review-thread feedback: typo fixes, clearer grammar, consistent terminology, and improved readability in the workaround guidance. Scope is limited to the commented section only.

• Problem statement alignment

  • Applied all requested edits from the linked review thread to the new FAQ content in README.md.
  • Kept changes strictly to wording/formatting issues called out in review.

• FAQ copy and terminology cleanup

  • Standardized terminology to “leaf node”.
  • Corrected wording and typos (principle, Note that, if, Connecting, and optionally rename).
  • Rephrased awkward sentences for clearer user-facing guidance without changing technical intent.

• Workaround list readability

  • Added punctuation/flow improvements (including by:) and consistent bullet style.
  • Kept both documented workaround options intact while making each item easier to scan.

This block cannot be disabled, but it can be circumvented by:
- Connecting the auth callout accounts on the leaves to a dedicated non-auth-callout-enabled account on the hub.
- Using import/export on the leaf node to export (and optionally rename) `$SYS.REQ.USER.AUTH` before routing to the hub.