docs(skills): say which package provides the experimental entry point (#153)

Corrects one sentence in the "Experimental features" section of
`packages/ai/README.md` (`launchdarkly-ai-python`).

The README said `launchdarkly_ai_server.experimental` is something "this
package installs". That isn't guaranteed. `packages/ai/pyproject.toml`
depends on an unpinned `launchdarkly-ai-server`. A user who upgrades
only `launchdarkly-ai-python` keeps whatever `launchdarkly-ai-server`
they already have installed or locked, because that version still
satisfies the requirement. The latest published release, 0.2.4, has no
`experimental` subpackage, so on it `import
launchdarkly_ai_server.experimental.skills` raises
`ModuleNotFoundError`. Nothing else breaks: `launchdarkly-ai-python` is
`from launchdarkly_ai_server import *` and never imports `experimental`.

The new text:
- says the features live in `launchdarkly-ai-server` and need a release
of it that includes them
- tells users to upgrade `launchdarkly-ai-server` itself if the import
fails

🤖 Generated with [Claude Code](https://claude.com/claude-code), updated
by @XieX

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Overview**
> **Documentation-only** update to the **Experimental features** section
in `packages/ai/README.md`.
> 
> The README no longer implies that installing `launchdarkly-ai-python`
always installs a `launchdarkly-ai-server` build with `experimental`. It
now states that experimental APIs live in **`launchdarkly-ai-server`**,
depend on a server release that actually ships them, and that **`import
launchdarkly_ai_server.experimental` failures should be fixed by
upgrading `launchdarkly-ai-server`**, not only the barrel
package—because the dependency is unpinned and an older server can
remain after upgrading `launchdarkly-ai-python`.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
167b370. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: XieX

packages/ai/README.md

@@ -76,8 +76,11 @@ result = await evals.run(
 
 ## Experimental features
 
-Experimental features are not re-exported from this package. Import them from
-`launchdarkly_ai_server.experimental`, which this package installs. For example, Agent Skills
+Experimental features are not re-exported from this package. They live in
+`launchdarkly-ai-server`, the package this one depends on, and need a `launchdarkly-ai-server`
+release that includes them. Import them from `launchdarkly_ai_server.experimental`; if that
+import fails, upgrade `launchdarkly-ai-server` itself, since upgrading this package alone can
+leave an older `launchdarkly-ai-server` in place. For example, Agent Skills
 lives in `launchdarkly_ai_server.experimental.skills`; see the
 [Agent Skills guide](https://github.com/launchdarkly/python-ai-sdk/blob/main/packages/client/README.md#agent-skills-experimental).