Design

Context

See proposal.md for motivation. Status sampling already calls a package-private EvelynPriceIndexCalculator, which holds the curve constants and decimal arithmetic. The implementation receives its canonical EVE/USDT pair from the Hub and validates storage only at startup. Constructor name reservations, file restoration and durable append behavior must survive the package move.

Goals / Non-Goals

Goals: Keep one calculation behind both the public reference-price operation and status sampling; preserve pure on-demand reads and separate Production/Test state while making their status-service identity explicit.

Non-Goals: No additional reference-data service, new ValueTags, curve configuration, lifecycle redesign, package-wide cleanup, trading activation, or storage provisioning/migration.

Decisions

Move only the API, implementation and calculator. Import EvelynStatusIndexPoint from its existing package. Retain the implementation's existing constructor shapes and lifecycle methods; a compatibility wrapper would leave two competing names and is unnecessary for the requested breaking rename.
Implement getReferencePrice(timestamp) as a direct call to the calculator's existing expected-price method, wrapped in AssetPrice with the constructor-injected trading pair. Sampling continues to call calculateIndex(actualPrice, samplingInstant), which delegates to that same expected-price method. Sharing the helper preserves identical constants and arithmetic without allocating a second service or changing index calculation.
Give the public operation no lifecycle gate, synchronization, clock read, ticker lookup or storage access. The immutable trading pair and pure calculator suffice before startup and during stop. Null and pre-start rejection are inherited from the calculator.
Rename Hub factory references, dependency fields, constants and process IDs together, and update Mission Control's parameter/field types. Process Manager already displays IDs from Hub snapshots and needs no new hardcoded mapping. Keep instance names Production and Test and the data/evelyn root.
Document the private configuration substitutions without editing the deployment configuration. The versioned example currently selects only Registry and Journal, so its selected processes stay unchanged.

Risks / Trade-offs

[Consumers using old packages or IDs fail] → Update all versioned consumers and document exact deployment substitutions; intentionally provide no alias.
[Fractional exponentiation uses floating-point transcendental arithmetic] → Preserve the existing calculator unchanged and check the start, annual and representative fractional values.
[Verification could trigger operational side effects] → Compile normally and use offline deterministic checks with fake Ticker and temporary storage; never run the Hub or financial processes.
[No existing status/calculator verification source is present in this checkout] → Add only the deterministic acceptance checks explicitly required by #88, covering the public API and regression behavior rather than the rename itself.

Migration Plan

Deploy the renamed code with evelyn.service.prod replaced by evelyn.status.prod and evelyn.service.test by evelyn.status.test wherever present in private conf/NenjimHub.conf. Preserve line order and enabled/commented selection. Retain existing status files byte-for-byte; the service reads the same paths and format. Rollback restores the old code and old IDs without a data migration.

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