Replace httpx and httpx-sse with httpx2 (modelcontextprotocol#2972)

Co-authored-by: Max Isbey <224885523+maxisbey@users.noreply.github.com>

Point pre-release install pins at 2.0.0b1 (modelcontextprotocol#3039)

Conformance burn-down: server-side InputRequiredResult, Mcp-Method/Na…

…me validation, x-mcp-header filter (14 scenarios → green) (modelcontextprotocol#2974)

[v1.x] Support TransportSecuritySettings in the WebSocket server tran…

…sport (modelcontextprotocol#2992)

Drop stale superset-leniency note from ElicitResult.content docstring (…

…modelcontextprotocol#2884)

[v1.x] Pass a list to parametrize in test_docs_examples (pytest 9.1.0…

… compat) (modelcontextprotocol#2889)

Update the v2 status banner and pin spawned environments to the runni…

…ng SDK version (modelcontextprotocol#2834)

[v1.x] Scope experimental tasks to the session that created them (mod…

…elcontextprotocol#2720)

[v1.x] refactor: import SSEError from httpx_sse public API (modelcont…

…extprotocol#2561)

[v1.x] fix: handle ClosedResourceError when transport closes mid-requ…

…est (modelcontextprotocol#2334)

Co-authored-by: Owen Devereaux <owendevereaux@users.noreply.github.com>
Co-authored-by: Max Isbey <224885523+maxisbey@users.noreply.github.com>