FOLLOW-UP: addClass:on:done inconsistency across datepicker/timepicker variants

[adnaan]

Context

This follow-up task was identified during the review of PR #292.

Source PR: #292
Suggested by: @claude[bot]

Task Description

lvt-el:addClass:on:done="open" is present in datepicker/range.tmpl, timepicker/default.tmpl, and timepicker/duration.tmpl but absent from datepicker/single.tmpl.

This means:

• Range datepicker + both timepickers reopen on every server response
• Single datepicker won't — which may cause a disruptive close during multi-step interactions

If the omission on single.tmpl is intentional (close-on-select UX for single picker), add a comment explaining the difference. If not, add the directive.

Also: any server-triggered re-render (including unrelated actions) will reopen the picker, which may be surprising.

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This issue was automatically created from PR #292 review comments.