Hide "for" on state condition when matching an attribute (#52710)

* Hide "for" on state condition when matching an attribute

The legacy state condition measures the `for` duration against
`last_changed`, which only updates on state changes, not attribute
changes. So `for` together with `attribute` is unreliable and core is
moving to reject it. Omit the `for` field when an attribute is selected,
drop any lingering duration value, and explain why via a helper.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* Keep "for" visible but disabled when matching an attribute

Removing the field left the explanation pointing at a control that was no
longer on screen. Keep "for" in the form, disable it while an attribute is
selected, and move the helper text under it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>