copilot_model_api_mode() called normalize_copilot_model_id() which
fetched the GitHub model catalog via HTTP, then the secondary endpoint
check fetched it again because the catalog was never passed through.
Fix: fetch the catalog once at the top of copilot_model_api_mode()
and pass it to normalize_copilot_model_id(). The secondary check
then sees a non-None catalog and skips the redundant fetch.
For a Claude model switch on Copilot this eliminates one 5-second-
timeout HTTP call from the interactive /model path.
Surfaced during review of PR #10533.
Co-authored-by: kshitijk4poor <kshitijk4poor@users.noreply.github.com>
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