refactor: rename SDK package from agoraio-sdk to agora-agent-sdk

Major refactoring to rename the Python SDK package from "agoraio-sdk" to "agora-agent-sdk" for better clarity and branding alignment. This change improves package naming consistency and removes outdated documentation.

Key changes:
- Rename package from "agoraio-sdk" to "agora-agent-sdk" in pyproject.toml
- Update SDK name header in client wrapper to use new package name
- Update version metadata import to use new package name
- Make TTS and LLM properties optional in StartAgentsRequestProperties
- Clear README.md content (temporary during restructuring)
- Update CLI version from 3.35.2 to 3.76.0 in metadata
- Update packaging dependency from 25.0 to 26.0

🌿 Generated with Fern

Author: fern-api[bot]

.fern/metadata.json

@@ -1,5 +1,5 @@
 {
-  "cliVersion": "3.35.2",
+  "cliVersion": "3.76.0",
   "generatorName": "fernapi/fern-python-sdk",
   "generatorVersion": "4.37.0",
   "generatorConfig": {