feat(runtime, react): Scaffold Intelligence runner and agent (CopilotKit#3348)

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## What does this PR do?

This PR adds an initial scaffolding of the CopilotKit Intelligence agent
runner and React agent classes.

Both will be part of the new threads-enabled feature set, and will be
iterated upon in subsequent PRs.

For this PR, the React agent is not tied into `useAgent`, so it cannot
currently be interacted with.

Also, in this PR, docs that describe the agent and runner architecture
are not updated, as it is assumed that these classes may change
substantially and rapidly in the very near term.

A big part of this PR is the integration of the Phoenix JS client SDK to
enable the IntelligenceAgent and IntelligenceAgentRunner to connect to
the Intelligence platform's Phoenix server. That allows threaded AG-UI
messages to be streamed from to and from the platform, instead of
directly from agent runner to client agent hook.

The message structure for the Phoenix connection is still in flux.

Note: while the SQLite-backed agent runner is in a separate package, the
IntelligenceAgentRunner was intentionally placed along side the
`ProxiedCopilotRuntimeAgent` to make it that much easier to switch from
the latter to the former if desired.

## Related PRs and Issues

- https://linear.app/copilotkit/issue/ENT-59
- https://linear.app/copilotkit/issue/ENT-54

## Checklist

- [x] I have read the [Contribution
Guide](https://github.com/copilotkit/copilotkit/blob/master/CONTRIBUTING.md)
- [ ] If the PR changes or adds functionality, I have updated the
relevant documentation

Author: BenTaylorDev

packages/v2/core/package.json

@@ -41,6 +41,7 @@
   "dependencies": {
     "@ag-ui/client": "0.0.46",
     "@copilotkitnext/shared": "workspace:*",
+    "phoenix": "^1.8.4",
     "rxjs": "7.8.1",
     "zod": "^3.25.75",
     "zod-to-json-schema": "^3.24.6"