fix: shorten methodology bullets under Zod 500/240-char caps

[Flotapponnier]

Fixes bench page 404s caused by Zod spec validation silently dropping specs with over-length strings.

pm-rate-limits.yml:

• methodology[0] (endpoint classes): 678 → 280 chars
• methodology[6] (ramp tiers): 623 → 230 chars

pm-ws-latency.yml:

• providers/kalshi/formula: 289 → 217 chars (removed redundant 403 sentence already in per_chain_explainer)
• methodology[5] (metrics): 551 → 420 chars