fix(billing): price Anthropic 1-hour cache writes separately

[atirna]

Summary

• Price Anthropic 1-hour cache writes at their 2x input rate while keeping 5-minute writes and aggregate-only payloads at 1.25x.
• Carry the reported 1-hour split through streaming and non-streaming cost calculation into billing debits.

Why

The aggregate cache-creation count currently prices every write at the 5-minute rate, including the 1-hour tier.

Verification

• Before, on current main: 10 fresh tokens plus 1M 1-hour cache writes at $5/M calculated to $6.250050 instead of $10.000050.
• After: go test ./internal/router/catalog ./internal/observability/otel ./internal/translate ./internal/billing -count=1 and go test ./internal/proxy -count=1 pass. The catalog test covers 1-hour, mixed-tier, aggregate-only, and inconsistent usage breakdowns.

Fixes #867

[devin-ai-integration]

Thank you so much for this, @atirna — this is a genuinely valuable fix. The 1-hour tier was silently under-billed, and you threaded the split through every surface (extractor, translator sink, handover usage, stream cost writer, billing debit) with careful edge handling (clamping, aggregate-only fallback, the web_search remainder). Really nice work, and make precommit was clean on your branch.

To match a couple of internal conventions I've re-opened it as #1203 with your code intact and you credited as co-author. This is not on you at all — these rules live in our AGENTS.md, keep evolving, and aren't obvious from the outside. The only deltas:

• Comments describe the invariant, not the task (AGENTS.md → "Concise comments, sparingly": never reference current task/PR/caller). The test comments in cost_test.go referenced issue billing: 1-hour TTL cache writes are billed at the 5-minute 1.25x rate, undercharging by 37.5% #867 and narrated the pre-fix number ("vs $6.25005 before"); they now just state the pricing rule being guarded. Issue links belong in the PR description (Fixes #867 is there).
• Consistent parameter order: routerCostCalculator / routerResponseCostFromPricing took the 1h count last, while catalog.EffectiveInputCost takes (cacheCreation, cacheCreation1h, cacheRead). I aligned them so the positional ints read the same everywhere.

Everything else — production logic, tests, structure — is exactly as you wrote it. Thanks again, and please keep them coming!