feat: make ollama host configurable in goose2

[kalvinnchau]

Category: fix
User Impact: Users can configure Ollama with a custom host or port from goose2 instead of having it appear connected by default.
Problem: goose2 treated Ollama as connected because the backend default host counted as configured, even when users had not saved any Ollama settings. That made it unclear how to use a non-default Ollama host or port.
Solution: Ollama now reports configured status only when OLLAMA_HOST is explicitly set, and goose2 exposes a host field pre-filled with the effective local default so users can save or edit it.

File changes

crates/goose/src/providers/ollama.rs
Overrides Ollama inventory configuration status so the runtime fallback host does not make the provider appear configured. Adds focused tests for unset, environment, and saved-config host states.

ui/goose2/src/features/providers/providerCatalog.ts
Changes Ollama from a local zero-config entry to a configurable provider with an OLLAMA_HOST field and default host value.

ui/goose2/src/features/providers/providerCatalog.test.ts
Covers the Ollama catalog entry so the host field and default remain present.

ui/goose2/src/features/settings/ui/ModelProviderRow.test.tsx
Adds coverage that provider field defaults are pre-filled and saved from the setup form.

ui/goose2/src/features/settings/ui/modelProviderHelpers.tsx
Uses provider field defaults when initializing setup drafts and no saved config value exists.

ui/goose2/src/shared/types/providers.ts
Adds an optional defaultValue property to provider field metadata.

Reproduction Steps

1. Open goose2 settings and go to model providers.
2. Expand Ollama before setting OLLAMA_HOST.
3. Confirm it is not shown as already connected and that the Host field is pre-filled with http://localhost:11434.
4. Change the Host field to a custom Ollama endpoint or keep the default, then save.
5. Confirm Ollama is marked connected and model inventory refresh starts for the saved host.

Screenshots/Demos

Not included. The UI change is a settings form field and can be verified with the reproduction steps above.

Verification

• cargo fmt
• pnpm exec biome format --write ...
• git diff --check
• git push -u origin HEAD pre-push checks passed, including goose2 pnpm test, pnpm check, pnpm build, Tauri cargo fmt --check, cargo check, and cargo clippy -- -D warnings.

before:

after:

[baxen]

LGTM