``set_dash_metadata`` can raise ``KeyError`` when a position layout node
is missing expected keys (e.g. ``node['meta']['chartId']`` on a malformed
CHART entry). Add ``KeyError`` to the ``(ValueError, TypeError)`` handler
so a corrupted source layout produces a structured error response instead
of an unhandled exception. Also add ``dashboard_id`` to the ctx.error
log message in this handler for consistency with all other error branches.
Add regression test ``test_key_error_in_copy_command_returns_structured_error``.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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