The pi-ai Anthropic provider constructs the full API endpoint as
`${baseUrl}/v1/messages`. If a user configures
`models.providers.anthropic.baseUrl` with a trailing `/v1`
(e.g. "https://api.anthropic.com/v1"), the resolved URL becomes
"https://api.anthropic.com/v1/v1/messages" which the Anthropic API
rejects with a 404 / connection failure.
This regression appeared in v2026.2.22 when @mariozechner/pi-ai bumped
from 0.54.0 to 0.54.1, which started appending the /v1 segment where
the previous version did not.
Fix: in normalizeModelCompat(), detect anthropic-messages models and
strip a single trailing /v1 (with optional trailing slash) from the
configured baseUrl before it is handed to pi-ai. Models with baseUrls
that do not end in /v1 are unaffected. Non-anthropic-messages models
are not touched.
Adds 6 unit tests covering the normalisation scenarios.
Fixes#24709
(cherry picked from commit 4c4857fdcb)
