docs: align plans and guides with the current product

[polly3223]

The docs currently say Pro includes confidential inference, describe removed Agent/admin screens, and include Agent API fields the released backend rejects. This pass aligns the guides with the current product and live Clerk catalog. It keeps the future pricing redesign out of the current-plan documentation.

• Clarify Basic / Plus $19 / Pro $99 / Confidential $119, separate sponsored access from paid billing, and explain six-hour/weekly usage windows. Pro alone does not include Confidential.
• Match the two approval modes and actual precedence: Allow everything bypasses Ask rules; Deny remains effective. Explain account defaults versus chat overrides consistently.
• Update Agents beta setup, configuration lifetime, delegated sessions, revocable sharing and schema-v2 API examples. Replace removed evaluations/webhook/version-history UI instructions with current availability and useful alternatives.
• Match the production admin views, released platforms, memory scope, exports and integration behavior. Remove unsupported shared-workspace and fixed processing-time promises.
• Remove the retired Telegram integration: delete the guide and Remote access navigation, clear Telegram references from current guides, and redirect old HTML/Markdown URLs to Chat. Dated release-note mentions remain historical.

Evidence baseline: backend 01d433396ef225d085abafe9993ebc1855fab213 from the October 6 production release manifest; frontend 1fc72ba8b8b209a94c087491b6055e7c0757f5e7; admin production 2e20d2cd3e7272b6e06ab168eca4125cd500dcc2; production Clerk catalog read October 8. Agents visibility remains beta/deployment dependent. All 54 original MDX pages were reviewed; 42 needed changes, including removal of the retired Telegram guide, plus navigation, diagram wording, redirects and AGENTS guidance. Telegram retirement is confirmed by the product owner; retained backend code is not evidence of availability.

Validation: production build / TypeScript / 164 static outputs; all 53 remaining MDX pages, 3,403 internal links, anchors and assets, and 30 JSON examples pass. Removed Telegram routes are absent from generated pages, navigation, search and LLM exports; all three new redirects return 301 and their destinations return 200 under local Cloudflare Pages. The original audit also checked Agent request/response examples against deployed Pydantic schemas, 14 desktop/mobile Chromium views and seven Markdown exports. No product writes or inference calls.

Review boundary: existing team-confirmed SOC 2 Type II, open-source-only and account-deletion policy statements are retained. This documentation audit does not independently certify effective provider overrides, third-party retention, or deletion across every store/backup. Dated release notes retain their workflow-managed history. No product runtime or billing behavior changes.