Use dedicated endpoint for Agents Manager state

[jom]

Partially fixes AI-850

Paired with Automattic/jetpack#46937

Proposed Changes

• Switches all Agents Manager API calls from the general /me/preferences endpoint to the new dedicated /wpcom/v2/agents-manager/state endpoint.
• Removes the calypso_preferences wrapper from all request and response handling — the new endpoint uses a flat key/value format.
• Updates four files:
  • resolvers.ts: GET now hits /agents-manager/state and reads flat keys directly instead of unwrapping calypso_preferences.
  • actions.ts: POST now hits /agents-manager/state with { state: { ... } } body instead of { calypso_preferences: { ... } }.
  • use-persisted-history.ts: Same POST pattern for persisting router history on navigation.
  • use-unified-ai-chat.ts: Now fetches from /agents-manager/state?key=unified_ai_chat (v2) instead of /me/preferences (v1.1).
• The Jetpack apiFetch path (/agents-manager/open-state) is unchanged — the Jetpack proxy handles the translation.

Why are these changes being made?

• The general /me/preferences endpoint exposes all calypso preferences, which is unnecessarily broad for Agents Manager.
• A dedicated scoped endpoint follows the principle of least privilege — the Agents Manager only reads/writes the keys it needs.

Testing Instructions

1. Test alongside Use Agents Manager state endpoint jetpack#46937
2. Calypso (wordpress.com):
   • Open WordPress.com, open Agents Manager, verify it loads correctly (state persisted).
   • Open DevTools Network tab, confirm requests go to /agents-manager/state (not /me/preferences).
   • Close and reopen Agents Manager — state should persist (open/docked/position). Note: There is a preexisting issue where the request happens multiple times because the router and open/closed state changes happen seperately.
   • Navigate within Agents Manager, refresh — router history should restore.
3. wp-admin (Atomic site):
   • In sandbox, run:
     • install-plugin.sh agents-manager update/use-dedicated-state-endpoint
     • install-plugin.sh help-center update/use-dedicated-state-endpoint
   • Sandbox widgets.wp.com
   • On dev WoA site, using Jetpack Beta plugin, switch to change/use-wpcom-agents-manager-endpoint.
   • Open wp-admin on an Atomic site with Agents Manager enabled.
   • Verify the panel opens/closes and state persists across page loads.
   • Confirm frontend requests still go to /agents-manager/open-state (the Jetpack proxy).
4. wp-admin (WPCOM site):
   • In sandbox, run:
     • install-plugin.sh agents-manager update/use-dedicated-state-endpoint (if not already)
     • install-plugin.sh help-center update/use-dedicated-state-endpoint (if not already)
     • bin/jetpack-downloader test jetpack-mu-wpcom-plugin change/use-wpcom-agents-manager-endpoint (Use Agents Manager state endpoint jetpack#46937)
   • Sandbox widgets.wp.com
   • Open wp-admin on an WPCOM site with Agents Manager enabled.
   • Verify the panel opens/closes and state persists across page loads.
   • Confirm frontend requests still go to new WPCOM public-api /agents-manager/state endpoint.
5. Unified AI chat flag:
   • For a user with unified_ai_chat enabled, verify the flag is correctly read on Calypso. Unified sidebar should load when the setting is enabled.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you tested accessibility for your changes? Ensure the feature remains usable with various user agents (e.g., browsers), interfaces (e.g., keyboard navigation), and assistive technologies (e.g., screen readers) (PCYsg-S3g-p2).
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-169558

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-169558&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-169558&env=a8c-for-agencies

Dashboard live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-169558&env=dashboard

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• agents-manager
• help-center
• notifications
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug update/use-dedicated-state-endpoint on your sandbox.