docs: align content with current implementations

[amavashev]

Summary

• audit and update 181 content documentation and blog files against the current protocol, runtime, admin, events, dashboard, client, plugin, and integration implementations
• distinguish implemented behavior from registered, historical, planned, or application-owned behavior across scopes, dry-run evaluation, caps, RISK_POINTS, runtime events, webhooks, tracing, and reserve/commit settlement
• refresh provider comparisons, pricing assumptions, MCP guidance, and voice-agent integration patterns against current authoritative sources
• preserve the root index.md homepage and exclude generated or non-content changes

Why

The documentation had accumulated stale or overly broad claims as implementations evolved. The main gaps involved native run scope assumptions, successful lifecycle event emission, live versus dry-run denial behavior, event payloads, correlation semantics, provider capabilities, and application responsibilities for authorization and external outcomes.

Impact

Readers now get implementation-aligned guidance with explicit boundaries between what Cycles currently enforces, what hosts must implement, and what remains planned. This PR changes documentation only; it does not modify product code or the homepage.

Validation

• npm test — 6 files, 93 tests passed
• npm run check:implementation-drift — matched 17 implementation sources
• npm run build — VitePress build and 9 PDF renders passed
• blog metadata audit — 122 posts, 0 issues
• external link crawl — 5,162 links, 905 unique, 0 errors after configured bot-block exclusions and manual verification of the Envoy documentation target
• git diff --check