feat: add governance action context

[haasonsaas]

Summary

• add governance.v1.ActionContext for magnitude-aware action evaluation and classification
• attach structured context to both EvaluateActionRequest and ClassifyRiskRequest
• update generated Go, TS, and Python artifacts plus governance contract fixture coverage

Testing

• buf lint
• buf generate --path proto/governance/v1/governance.proto --timeout 10m
• go test ./... -count=1
• npm ci && npm run check:package
• python -m build (blocked locally: build module not installed in this environment)

Part of #25

[cursor]

PR Summary

Medium Risk
This is a wire-level proto change adding new request fields, so it requires coordinated client/server regeneration and rollout to avoid compatibility issues across services.

Overview
Adds a new structured governance.v1.ActionContext message (record count, currency amount/code, environment, data classification) and includes it on EvaluateActionRequest and ClassifyRiskRequest.

Regenerates Go/Python/TS protobuf artifacts and updates the governance evaluate_action_request.json fixture plus contract_test.go assertions to cover the new context fields.

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