feat(background_review): make review-fork toolsets config-overridable

[Wetnesday]

What

Makes the background skill-review fork's toolsets config-overridable via background_review.enabled_toolsets (and .disabled_toolsets) in agent/background_review.py.

Default behavior is unchanged: when the config keys are absent, the fork inherits the parent agent's toolsets exactly as before (so the request tools[] stays byte-identical for Anthropic prefix-caching).

Why

The review fork inherits the parent's full toolset so tools[] is byte-identical for cache parity. But on a provider with a hard tool-count cap — e.g. xAI/Grok's 200-tool limit — once enough MCP servers are enabled, the inherited set exceeds the cap and the review request 400s (N tools provided, maximum is 200), so the fork never runs and no skill is produced.

Since the runtime whitelist already restricts review dispatch to memory/skills, a narrower request set is lossless. This adds an opt-in escape hatch for capped providers without changing anything for Anthropic.

Behavior change

None unless background_review.enabled_toolsets is set in config. The config read is wrapped in try/except and falls back to the previous getattr(agent, "enabled_toolsets", None) inheritance.

Example config

background_review:
  enabled_toolsets: [memory, skills]   # pin the fork under a provider tool cap

[teknium1]

Thanks for targeting the review-fork schema cap without changing the default cache-parity path. Current main still forwards the parent toolsets to the fork at agent/background_review.py:711-712, so the requested capability is not superseded.

Problems

• The patch reads top-level background_review, but the established review configuration is auxiliary.background_review in hermes_cli/config.py:1723 and is consumed by agent/background_review.py:77-82. This would split review settings across two namespaces.
• The PR changes only agent/background_review.py; it has no regression test for configured overrides or the fallback to parent toolsets.

Suggested changes

• Add the two keys under auxiliary.background_review in DEFAULT_CONFIG, read that existing mapping, and document the setting beside the current background-review configuration.
• Add constructor-capture coverage for override and absent-key fallback behavior.

Current main has refactored this constructor for resolved runtime metadata in 97e9c64664, and GitHub reports this branch as conflicting, so salvaging should transplant the logic into that current path.

Automated hermes-sweeper review.