fix: add provider hook for OpenCode >=1.14.49 model listing API (#12) (#16)

* fix: add provider hook for OpenCode >=1.14.49 model listing API

OpenCode 1.14.49 introduced the v2 model/provider listing API (ProviderHook)
as the canonical way to supply models. PR #14's fix only set models in the
config hook, which is ignored on 1.14.49+.

- Add ProviderHook types to custom type declaration
- Implement provider.models() callback that fetches /v1/models via ctx.auth
- Keep config hook eager-fetch for <=1.14.48 backward compat
- Add 3 regression tests for provider hook

* chore: remove unnecessary type assertion in provider hook fallback

* fix: align provider model type shim

* fix(provider): always return own defaults when unauthenticated

* style(types): add blank line between ProviderHook and Hooks interfaces

* test(provider): verify stale models are ignored when unauthenticated

* chore(release): bump version to 1.1.4

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Co-authored-by: Sebastian Rumpf <alp4d0g007@googlemail.com>