docs(openrouter-analytics-schema): sync with openrouter-web changes

[devin-ai-integration]

Summary

openrouter-web PR #28910 added a new analytics metric, blended_cost_per_million_tokens, to MetricNameSchema and the metric registry. The public meta endpoint (get-meta.ts → buildMetricsMeta()) sources its metric list from that registry, so the metric is now discoverable and queryable via the public analytics API — but the openrouter-analytics-schema skill's enumerated Cost-metrics list didn't include it.

Adds it under Cost metrics:

- `blended_cost_per_million_tokens` — blended inference cost per 1M tokens:
  (sum(usage) + sum(byok_usage_inference)) / (prompt_tokens + completion_tokens) * 1e6 (up to 365 days).
  A rate metric (is_rate: true, display_format: currency) — averaged across the range, not summed.

No other sections changed; format/style preserved.

Link to Devin session: https://openrouter.devinenterprise.com/sessions/096e84df73bc4f0f9bf1b5f26a0cf661

[devin-ai-integration]

Original prompt from Automation

You are the public skills sync pipeline. Your job is to scan PRs merged to main on OpenRouterTeam/openrouter-web in the last 24 hours, determine if any changes warrant updating the public agent skills in OpenRouterTeam/skills, and open PRs to the skills repo when updates are needed.

#``# Step 1: Identify relevant merged PRs

Clone both repos:

cd /home/ubuntu/repos/openrouter-web
git fetch origin main
git log --since='24 hours ago' --merges --first-parent origin/main --pretty=format:'%H|%s' --name-only

For each merged PR, collect the list of changed files. Only PRs that touch the paths in the mapping below are relevant. Skip bot commits (devin-ai-integration[bot], Devin AI, GitHub Actions Bot, openrouter[bot], opencode-agent[bot], OpenRouter SDK Bot, Claude, detail-app[bot], forge-the-devex-intern[bot], dependabot[bot]).

If no relevant PRs were merged, post a short message to the #devrel Slack channel (C08LQFVSC7Q) saying no skill-relevant changes were detected today, and exit.

#``# Step 2: Map changed files to affected skills

Use this mapping to determine which public skills are potentially affected:

openrouter-web paths	Affected skill(s) in OpenRouterTeam/skills
sdks/typescript/, packages/llm-interfaces/	openrouter-typescript-sdk, openrouter-agent-migration
services/cfw-*/src/routes/*analytics*, analytics query/response schemas	openrouter-analytics, openrouter-analytics-query, openrouter-analytics-schema
Generation routes, /api/v1/generation	openrouter-generations
Image generation adapters, packages/image-generation/	openrouter-images
supabase/seeds/, model schemas, /api/v1/models route	openrouter-models
OAuth/auth routes, PKCE flow code	openrouter-oauth
STT adapters, services/cfw-stt-api/, /api/v1/audio/transcriptions	openrouter-stt
TTS routes, /api/v1/audio/speech	openrouter-tts
Video adapters, /api/v1/videos	openrouter-video
``@`openr... (3383 chars truncated...)

[devin-ai-integration]

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