The earlier enterprise base URL change (proxy-ep parsing) gave us URLs
like `api.enterprise.githubcopilot.com`, but ~15 host-matching call
sites still hard-coded `api.githubcopilot.com`. Enterprise users would
therefore drop the `Copilot-Integration-Id: vscode-chat` header at
client-build time, and upstream rejected requests with:
The requested model is not available for integrator "zed"
(or "copilot-language-server") — verify the correct
Copilot-Integration-Id header is being sent.
The header was correct in copilot_default_headers(); it just never
made it into default_headers for non-default hostnames because every
detector compared against the exact string "api.githubcopilot.com".
This commit broadens all those checks to "githubcopilot.com" via
base_url_host_matches (which already does proper subdomain matching),
so api.enterprise.githubcopilot.com, api.business.githubcopilot.com,
etc. all share the same headers, vision routing, max_completion_tokens
selection, and reasoning-effort detection as the default endpoint.
Also adds ".githubcopilot.com" to _URL_TO_PROVIDER so context-window
resolution via models.dev works for enterprise base URLs, and tightens
_is_github_copilot_url to use suffix matching instead of strict equality.
Tests:
- New: enterprise Copilot endpoint preserves Copilot-Integration-Id
- New: enterprise endpoint returns max_completion_tokens (not max_tokens)
- Existing 333 base_url / copilot / aux-client / credential-pool tests pass
Parts 5 of #7731.
fb07215844