docs: replace stale launchdarkly-ai package name with launchdarkly-ai-python

[andrewklatzke]

Summary

• The convenience barrel was renamed to launchdarkly-ai-python; docs still told readers to pip install launchdarkly-ai / launchdarkly-ai[otel], which is not published on PyPI.
• Updated all remaining bare launchdarkly-ai references to launchdarkly-ai-python across the root README/AGENTS.md, the core client README/agents guide, the barrel agents guide (including the stale src/launchdarkly_ai/ path), and every handler agents.md OTel install snippet.
• Left valid sibling package names alone (launchdarkly-ai-server, launchdarkly-ai-*-agents, etc.). Both launchdarkly-ai-python[otel] and launchdarkly-ai-server[otel] remain documented where appropriate.

Test plan

• Repo-wide search for bare launchdarkly-ai (not followed by another package segment) returns no matches
• Spot-check README quickstart + one handler agents.md OTel section render correctly
• Confirm packages/ai/README.md was already correct and unchanged

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Note

Overview
Documentation is updated so install and architecture references match the published convenience barrel launchdarkly-ai-python instead of the obsolete bare launchdarkly-ai name (including launchdarkly-ai-python[otel] for OTel extras).

Root README.md and AGENTS.md now describe the Tier 0 barrel and consumer imports as launchdarkly-ai-python / launchdarkly-ai-server, with quick-start pip examples corrected.

packages/ai/agents.md is retitled for launchdarkly-ai-python and points to src/launchdarkly_ai_python/__init__.py as the re-export entry.

packages/client/README.md and every handler agents.md (claude, langchain, openai) plus packages/client/agents.md update OTel setup text so init_client() is documented as coming from launchdarkly-ai-server or launchdarkly-ai-python. Sibling packages such as launchdarkly-ai-server and handler wheels are unchanged.

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