[Improve] Restore the Auto tool approvals experimental setting

[daniel-lxs]

What changed

Restores the Auto tool approvals switch in Settings → Experimental, which #3180 hid. The component and its test come back as they were, and the control is registered again in the experiment settings list (experiment-settings-controls.tsx) under the experiment's existing customer-preview audience, so it appears on the Experimental page and not on the internal Nightly page.

Why this change was made

The switch was hidden because Auto was asking for approval on harmless reads. #3185 fixed those decisions (request context, judgment criteria, read content, and a credential scan), so the switch can be offered again.

Impact

Admins can turn the Auto tool approvals experiment on or off again from Settings → Experimental. The experiment stays off unless an admin turns it on; nothing about the experiment's default or gating changes.

How it was tested

• Settings page and Auto-related web tests: 10 files, 23 tests passed.
• @roomote/web type check, oxfmt, and oxlint on changed files passed.

[roomote-community]

No code issues found. See task

_{Reviewed 130035b}

[daniel-lxs]

Closing: the Auto tool approvals switch now lives under Nightly Experiments (#3207), so restoring the old experimental setting is no longer needed.