Platform usage counts are reported to PostHog only, not pushed to Autumn

Context

A daily job (billing-usage-report-service.ts, reportAllPlatforms) aggregates per-platform usage counts — active flows, team projects, active users — for every licensed platform. Until this decision the job had two sinks: a PostHog total_runs_per_day snapshot event (read by the console's usage cards) and an Autumn push (reportUsageCounts on the billing provider → balances.update per feature) meant to populate the usage column next to each limit in the Autumn dashboard.

The Autumn leg never worked and nothing consumed it:

• The instance holds only a customer-scoped Autumn key, and scoped tokens are allowlisted to check, track, customers.get, and entities.get (per Autumn's keys.mint docs). balances.update is not callable with one — the same 403 already recorded in decision 000013 for the abandoned seat-usage backstop. The client is constructed with failOpen: true, so the failing writes were swallowed silently.
• Enforcement never reads Autumn-side usage: limits are projected from plan grants (mapAutumnFeaturesToPlatformPlan reads granted), and the checks run against the AP database (decision 000013). Seat billing reads includedGrant/prepaidGrant, never usage.
• The console's usage views read the PostHog snapshots, not Autumn.

Decision

Report usage counts to PostHog only. The Autumn leg is removed end-to-end: reportUsageCounts is dropped from the BillingProvider interface (and its CE no-op and Autumn implementation), and setUsage/balances.update is dropped from the instance-side Autumn client wrapper (autumnUtils.client).

Consequences

• The Autumn dashboard shows no usage next to activeFlowsLimit / teamProjectsLimit / usersLimit for a customer. Support and sales read usage from the console's instance-reported usage cards (PostHog-backed) instead.
• One less silently-failing network call per platform per day; the PostHog capture in the same loop is unchanged.
• If Autumn-side usage is ever wanted, the scoped-key-compatible options are a read-then-track delta (both operations are on the scoped-token allowlist) or proxying balances.update through the console's master key — rejected for now as pure cost with no consumer.