* feat(agent): list created agents in sidepanel target catalog
* feat(agent): show created agents in sidepanel selector
* feat(server): add sidepanel chat route for created agents
* feat(agent): route sidepanel agent sends by agent id
* chore(agent): retire virtual sidepanel acp targets
* fix: address review feedback for PR #865
* feat: improve rate limit UX, usage page, and provider selector
- Show "Add your own provider for unlimited usage" CTA when BrowserOS
credits are exhausted or daily limit is reached
- Fix credit exhaustion detection to match actual error message
- Improve Usage page: remove disabled Add Credits button, add "Coming
soon" badge, add "Want unlimited usage?" section linking to providers
- Add "+ Add Provider" button at bottom of chat provider selector dropdown
* fix: use asChild pattern for Button+anchor in usage page
Replace nested <a><Button> (invalid HTML) with Button asChild
pattern per shadcn/ui convention.