Consolidate reusable prefab, model-adapter and checkpoint improvements #355

Category consolidation

Requested by Joel Z. Leibo in issue #373. This is the single continuing issue for this category. Implementation and subsequent improvements stay in PR #356. Approved PRs #297, #302, #304 and #332 are exempt and remain unchanged.

Scope

• Publish complete checkpoint JSON through same-directory atomic replacement, preserving a previous file on serialization or I/O failure.
• Share the existing optional-context assembly between basic and minimal prefabs, and retain the normal Concat name-prefix option.
• Add opt-in timeout/output bounds and JSON response schemas to the existing Ollama adapter. Default behavior remains unchanged.

These are existing-library improvements extracted from the Bellwether stack, not game-specific mechanics. The human acting-policy prerequisites remain separately approved in PRs #302 and #304. Approved checkpoint-input ownership #332 and viewer #297 remain untouched.

Consolidated review history

No additional standalone PR in this category; prerequisite pieces are extracted from the former Bellwether stack.

Superseded issues and PRs retain their original descriptions and point here. Consolidation closes duplicate review threads, not claims that pending code has landed upstream.