Embedder-segment quick start near top of README + fix silent weekly-health cron

[karlwaldman]

1. LNG/TTF/JKM/EUA/bunker first appear ~line 278 — a maritime-compliance or fleet-SaaS dev (our Refactor: Extract duplicate retry logic into shared strategy class #1 ICP per 2026-07-03 analysis) never sees themselves in the first screen. Add a "beyond oil" quick-start block up top (Brent/WTI examples can stay first, but the breadth should be visible without scrolling).
2. weekly-health.yml failed every scheduled run through Jun 1 and has been SILENT since — it's the only automated SDK-vs-API drift instrument. Repair or replace (relates to open Q1 monitoring issues [Q1-P0] Add integration tests against real production API #14/[Q1-P0] Add monitoring and alerting for SDK health metrics #19).

[karlwaldman]

Closed by PR #47. NOTE the bigger find from that work: the OILPRICEAPI_TEST_KEY repo secret exists but resolves EMPTY at runtime — live jobs now pass loudly with a ::warning:: instead of silently testing nothing, but real live coverage needs Karl to re-populate the secret (dedicated free-tier test account recommended, same key can go to oilpriceapi-node + oilpriceapi-go which share the pattern). Also: GitHub had auto-disabled the weekly cron for inactivity — re-enabled, next run Monday 14:00 UTC.