fix: stop a partial [providers.local] from deleting the local provider

The synthesis guard tested key membership, so a [providers.local] that set
only an api_key claimed the slot, blocked the bare base_url from filling
it, then failed the URL check and vanished. Losing the local provider is
the one outcome this feature cannot have. The guard now tests the URL and
merges, so the table adds detail to the local provider rather than
replacing it.

A filter given as a bare string was iterated character-wise, turning
filter = "qwen" into four needles that match almost every model id. Both
failures were silent, which is what made them worth fixing now.

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

0 files changed, 0 insertions, 0 deletions