[Work Packet]: Make compact health lookups truly lightweight

[juscghwe]

Goal

Make compact health responses actually use compact collection logic instead of collecting full subsystem metadata and discarding most of it before sending the response.

Compact health should be meaningfully cheaper and more responsive than detailed health.

Suggested branch name

backend/compact-health-lightweight

Expected task size

Small: one focused session

Scope

• Review compact health response flow.
• Identify places where detailed metadata is gathered before being reduced.
• Add or adjust lightweight health lookup paths for compact responses.
• Preserve detailed health behavior for diagnostic endpoints.
• Keep output contracts clear between compact and detailed modes.

Explicit non-goals / boundaries

• Do not remove detailed health diagnostics.
• Do not redesign all health endpoint contracts.
• Do not add frontend health UI work here.
• Do not optimize prematurely beyond avoiding obvious unnecessary metadata collection.

Files / areas likely affected

• backend/src/health
• backend routes for health endpoints
• health summary/compact helpers
• backend health docs
• backend tests or smoke checks

Definition of done

• Compact health lookups avoid collecting unnecessary detailed metadata.
• Detailed health lookups still expose diagnostic metadata.
• Compact and detailed response contracts remain documented or obvious from code.
• Local validation shows compact health still reports correct overall state.
• Any further performance ideas are captured separately.

Validation

• Run backend health endpoints in compact and detailed modes.
• Compare code paths to confirm compact mode uses reduced collection, not only response trimming.
• Run existing backend checks/typecheck/lint as available.

Follow-up ideas

• Add timing/performance assertions later if health checks become expensive.
• Add frontend loading-state behavior once frontend health checks are implemented.