feat(api): add OpenAI Decisions endpoint

[mudler-agent]

Description

Add POST /v1/decisions as an OpenAI-compatible REST adapter over LocalAI's existing SystemOne execution. No new inference backend or internal HTTP round trip.

• Translate predicate, typed choice, and score questions into SystemOne requests and return ordered answers.
• Share native/NER execution with /v1/systemone; preserve its existing API.
• Preserve boolean versus string choices, optional question names, empty score labels, and zero-valued results. Derive scores from the returned probability distribution.
• Apply the existing Decisions permission and usage middleware. Validate malformed backend answers before recording usage.
• Publish the route in Swagger and the existing systemone instruction group; document examples and compatibility limits.

Notes for Reviewers

This is a local execution adapter, not access to OpenAI's hosted model. Confidence retains local SystemOne semantics. Images reuse existing inline-image validation and backend limits; message text and images are flattened into the existing request format. Unsupported image detail settings are rejected. safety_identifier is accepted as compatibility metadata, not an identity or hosted safety service.

Usage reflects backend-reported counts. Detailed token-accounting objects can be empty when the backend does not provide those fields. Swagger 2 uses documented loose placeholders for JSON unions; runtime choice values remain strings or booleans.

Verification run independently after implementation:

go test ./core/schema ./core/http/auth -count=1
go test -tags auth ./core/schema ./core/http/auth -count=1
go test ./core/http/endpoints/localai -run TestLocalAIEndpoints -count=1
go test ./core/http/routes -run TestRoutes -ginkgo.focus='Decisions|SystemOne' -count=1
go test -tags auth ./core/http/routes -run TestRoutes -ginkgo.focus='Decisions|SystemOne' -count=1
git diff --check

All passed. Tests use a fake backend and exercise HTTP routing, permissions, accounting, conversion, and SystemOne regressions. Protobuf sources were generated and an ignored minimal UI embed fixture supplied for Go route tests. No full native build, GPU inference, or real-model validation was performed.

Swagger was regenerated with github.com/swaggo/swag/cmd/swag@v1.16.6; route/schema references were validated. Changes add only this route and its related definitions.

Signed commits

• Yes, I signed off my commits (DCO).
• Documentation updated (docs/content/).

AI assistance is recorded in the commit trailers.