`SessionContext._start` builds `ClientSession`'s `read_timeout_seconds` twice,
once for stdio and once for SSE and streamable HTTP, each with its own inline
`timedelta(...) if ... is not None else None`.
Move that to `_read_timeout`. ADK carries every timeout as float seconds and
now converts once, at the boundary where the SDK is called.
This is a plain de-duplication today. It also isolates a difference between
MCP SDK versions: 1.x types `read_timeout_seconds` as a `timedelta` and 2.x
types it as a float, so the conversion is the only line that has to change.
The explicit `is None` check is deliberate. A zero timeout is a real value, not
a missing one, and a truthiness check would silently turn it into "no timeout".
Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 968580764
Kathy Wu
574da43d65