perp audit batch 1: data sources + hygiene

[Flotapponnier]

Audit follow-ups, all verified before changing:

• DefiLlama source v3: HTML scraping (Cloudflare 403) replaced by the 2 free JSON overview calls (fees30d + OI for all venues at once). Perp volume went behind their paid plan, so the source stops publishing volume and the /perps hub derives volume30d from our own perp_venue_volume_24h_usd history instead.
• edgeX: getMetaData worked but all 292 getTicker calls got 429 from the VPS IP while residential passes (verified both). Source client now routes through COHORT_PROXY_URL; volume/OI are not latency numbers so a proxy is methodologically neutral.
• Hub: drift row dropped (parked venue, ghost seed), variational dropped (api.variational.io NXDOMAIN, omni 403, llama volume paywalled: no live source left).
• perp-funding: sample_size counted series (always 3); now count_over_time on the ETH hold gauge.
• perp-funding-stability: deribit removed (its funding series no longer exists), methodology note on young venues reading artificially stable (Polymarket constant funding since launch).
• Vertex checked and NOT touched: native archive still updates tick to tick despite the Ink acquisition.

63 specs valid, harness builds, tsc clean.