[core-shrink] upstream: cost ledger module (types, period budgets, reports) in tinyagents-harness #88

New module tinyagents-harness/src/cost/ledger/ beside turn_cost/model_budget:

• types from OpenHuman platform/cost/types.rs (TokenUsage, UsageScope, CostRecord, CostSummary, DailyCostEntry, BudgetStatus, CostDashboard), unified with CostTotals/CostSource/UsageRollup, keeping serde names for on-disk compatibility;
• budget.rs::evaluate (period evaluator; not the live Reservation limiter);
• report.rs group-by/cache-hit report with route_for_model as a callback;
• the in-memory daily/monthly/session aggregation from tracker.rs/rpc.rs, written against a LedgerStore trait (append, records_between).
  Coordinate the f64 USD vs ChargedAmount micros question with [inference-out] upstream: billed usage, response conversion, reasoning-effort parsing and sentiment prompt in tinyinference-llm tinyinference#9 (billed usage, under Epic: move inference/ out of the host into tinyinference, tinyagents and tinyjuice tinyhumansai/openhuman#8092) before fixing the record type. Host adoption: [core-shrink] adopt: cost ledger from tinyagents-harness openhuman#365.

Rows (from the tinyhumansai/openhuman#7390 audit)

Paths are relative to crates/openhuman-core/src/ in tinyhumansai/openhuman.

Blocked by

None.

Definition of done

• The capability lands in this repo with the tests that covered it in OpenHuman (moved, not copied), and is released/tagged so OpenHuman can pin it.
• This repo's own CI is green (build, tests, clippy).
• The OpenHuman host-adoption leaf can then delete the rows above (gitlink bump, plus digest re-pin for a loadable module).

Agent brief

• Files to consider: the rows above (OpenHuman side) and the target crate named in the description.
• Research: the gaps and decisions listed in the description; read each row's file before changing it.
• Workflow: one implementing-an-epic step on the epic branch. Follow openhuman's .claude/skills/migrate-to-submodule: upstream PR here first, then release/tag, then the OpenHuman gitlink bump (and digest re-pin) in the host leaf.
• Subagent: tdd-implementer.
• Dependencies: the Blocked by list above.

Parent: tinyhumansai/openhuman#7390