refactor runtime flows and align docs after audit loops

[iam-brain]

Summary

• simplify runtime hot paths by unifying request-transform wrappers, hardening auth storage/account selection behavior, and centralizing shared helpers
• fix audit-driven correctness/privacy issues (catalog fallback token handling, snapshot redaction for headers/meta/query, quarantine retention ordering, toggle message targeting)
• align user/development docs with current runtime behavior, logging/privacy semantics, and installer/config path details

Verification

• npm run verify
• focused regressions:
  • npx vitest run test/model-catalog.test.ts test/request-snapshots.test.ts test/quarantine.test.ts test/storage-corruption.test.ts

Notes

• includes two logical commits:
  1. refactor(runtime): simplify auth and transform pipelines
  2. docs: align guides with refactor and privacy behavior