raise without from discards exception chain in 12 remaining sites

[blackwell-systems]

Initial Checks

• I confirm that I'm using the latest version of MCP Python SDK
• I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue

Description

Follow-up to #2541 (fixed in #2542). The same pattern exists in 12 additional sites across 7 files. Each catches an exception and re-raises a new one without from, discarding the original traceback and __cause__.

Sites:

File	Line	Caught	Raised
client/session.py	346	ValidationError	RuntimeError
client/session.py	348	SchemaError	RuntimeError
client/auth/utils.py	246	ValidationError	OAuthRegistrationError
client/auth/utils.py	339	ValidationError	OAuthTokenError
server/auth/middleware/client_auth.py	83	ValueError/UnicodeDecodeError/binascii.Error	AuthenticationError
server/mcpserver/resources/types.py	75	Exception	ValueError
server/mcpserver/resources/types.py	151	Exception	ValueError
server/mcpserver/resources/types.py	196	Exception	ValueError
server/mcpserver/resources/types.py	205	Exception	ValueError
server/mcpserver/resources/resource_manager.py	96	Exception	ValueError
server/mcpserver/resources/templates.py	133	Exception	ValueError
server/mcpserver/prompts/base.py	185, 189	Exception	ValueError

Impact

Same as #2541: without from, Python shows "During handling of the above exception, another exception occurred" instead of "The above exception was the direct cause of the following exception." Callers cannot inspect __cause__ to determine the root cause programmatically.

The codebase already uses from correctly in server.py:451, server.py:459, server.py:1112, func_metadata.py:216,265, and tools/base.py:119. These 12 sites are the remaining inconsistencies.