feat: expose native MCP resource pages and reads - #5597

Summary

This pull request adds the missing native Session APIs for MCP resource pages and URI reads: list_mcp_resources, list_mcp_resource_templates, and read_mcp_resource. Each list call returns one page and its cursor. Typed results preserve text, blobs and metadata; callers decide whether to include resource contents in a prompt.

The methods reuse native MCP connections and the existing ownership of idle operations. Resource-only servers can use tools=[]; access starts only the requested server. Missing resource capability returns an empty page. Saved resource-only selections resolve against current declarations without granting tools. Cancellation and close join pending native work.

A patch to the pinned native codec preserves fractional resource annotation priorities. Valid replies with those values previously decoded as the wrong result type. Native pins stay fixed. The generated API snapshot includes the additive resource methods and types.

Test plan

• Full code-change verification passed: formatting, lint, mypy, Pyright, 5,602 parallel tests and 53 serial tests; 250 skips.
• All 11 resource tests passed across HTTP and stdio, including pagination, capability checks, error recovery, replacement/restore, cancellation and caller-owned results.
• A forced cp1252 stdin probe preserves the Unicode cursor after the stdio fixture reads UTF-8 JSON bytes. A focused run passed 358 tests across resources, MCP, checkpoint upgrades, write/network policy and A2A.
• A fresh wheel installation outside the checkout passed native qualification, resource page/read checks, and restore checks for narrowed and fully deselected servers. Codec compatibility and regression probes passed.
• Both required independent final reviews are clean on the verified source.

Issue number

None linked.

Checks

• I've added new tests, if relevant
• I've run the applicable checks in AGENTS.md, including .agents/skills/code-change-verification/scripts/run.sh when required
• I've confirmed all required local checks pass
• I've completed the review required by AGENTS.md