docs: nest soft-delete section under Advanced quota check and trim verbosity

## Problem

The `Free quota held by soft-deleted Cognitive Services accounts` section in [README.md](../README.md) is verbose (~55 lines) and lives as a sibling of `Advanced: check Claude quota & capacity programmatically`, even though both sections cover *quota* topics and read better together. The troubleshooting table also re-explains the same content in a long inline row that duplicates what the linked section already says.

## Proposal

- Nest the soft-delete section **inside** the existing `Advanced: check Claude quota & capacity programmatically` `` block so the two quota topics live together.
- Trim it to a short **fix + caveats** (list/purge commands kept; long prose removed).
- Match the README's established `...` pattern for a "main section heading, collapsed" feel.
- Tighten the troubleshooting row that re-explained the same thing to a one-liner pointing at the section.
- Preserve the existing anchor id `#free-quota-held-by-soft-deleted-accounts` so all cross-links keep working (referenced 3× from the troubleshooting table).

## Outcome

- Net **-17 lines** in `README.md` (+40 / -57).
- Single source of truth for soft-delete remediation, co-located with the rest of the quota guidance.
- All existing cross-links continue to resolve.

PR: see linked PR for the change.