feat(finops): mirror daily typed cost evidence

[routeplane-ops]

Summary

Mirror daily typed-cost evidence in Python models and exports at totals, day, model and key levels without changing resource methods. Implementation evidence: routeplane-core/routeplane#1135; initiative: routeplane-core/docs#625.

The additive outer field is optional for older gateways using Python-3.9-compatible TypedDict inheritance, without new dependencies. Nested evidence preserves required nullable fields, estimate-only states, provenance/coverage and bounded diagnostics. Missing evidence stays absent; legacy cost_micro_usd never supplies a typed amount. No new endpoint, billed/reconciled authority, deployment or PyPI release.

Validation

• Full local Python suite: 316 passed.
• Ruff source/test lint and format checks passed; mypy passed for all 21 source files.
• Thirteen standalone strict consumer probes passed, including eight invalid-shape rejection probes and tagged-union narrowing. These additional probes were local, not added as a new hosted workflow.
• Independent source correctness/security reviews passed on final diff SHA256 bf40a5e7613868962aad85bea2bea20c243e2c782007ecb5217a683c1582205c, including the final diagnostic-fixture refinement.
• Protected hosted CI across Python 3.9–3.13 remains required. TypedDicts are descriptive, not a runtime authenticity or numeric-bound validator.

Only models/exports and existing resource tests changed; no dependency, version, workflow or resource-method edits.

Closes #17