fix(mcp): follow nextCursor in prompts/list, resources/list and resources/templates/list

[yudongyouqing]

Summary

• New raven/mcp/paging.py walks a paginated list verb page by page with params=PaginatedRequestParams(cursor=...), stopping on an absent or a repeated cursor (the rule fix(mcp): page through tools/list nextCursor #825 introduced for tools/list). The public surface is one typed walker per verb (walk_tools / walk_resources / walk_resource_templates / walk_prompts), so the items a caller loops over carry their real SDK type rather than the Any a session yields at these call sites; the page shape stays behind one private engine.
• The three remaining verbs now walk through it: resources/list and resources/templates/list in raven/mcp/resources.py, and prompts/list in raven/mcp/prompts.py. Each site keeps its existing _with_timeout around the whole walk, so a server that never stops paging fails visibly instead of stalling the turn.
• The tools/list loop from fix(mcp): page through tools/list nextCursor #825 in raven/mcp/client.py collapses onto the same helper, so all four verbs share one implementation.
• Design note, for the author to settle: the module exposes one typed walker per verb over a single private engine, rather than one generic helper. Typed returns give the items their real SDK type (IDE completion, and future-proof the day an attribute rule switches on); under the repo's current ty config, a call-correctness gate with unresolved-attribute off, both shapes pass identically, and collapsing the wrappers into one generic helper is a small change if that reads better.
• Single-page behaviour is unchanged: existing tests pass without modification beyond the fakes accepting the params argument the walker always passes.

Type

• Fix

Verification

• Relevant tests pass locally: uv run pytest tests/test_mcp_resources.py tests/test_mcp_prompts.py tests/test_mcp_client.py tests/test_mcp_manager.py -> 88 passed, including four new tests (multi-page resources, multi-page templates, repeated cursor, multi-page prompts)
• The new tests fail on current main: stashing only the raven/ changes and running them -> 4 failed; restoring the fix -> pass
• Relevant lint / type checks pass locally: ruff check + ruff format --check on the touched files; ty check at the pre-change baseline (18 platform-only diagnostics on Windows, no new); lint-imports -> 10 contracts kept, 0 broken
• User-facing docs or screenshots are updated when needed: not needed, no user-visible copy changes

Risk

• Security impact considered: reads more of what a server already serves; no new inputs, credentials or surfaces
• Backward compatibility considered: single-page servers answer one request exactly as before, and the repeated-cursor stop rule is the one fix(mcp): page through tools/list nextCursor #825 already shipped for tools
• Rollback path is clear: plain revert restores the single-page behaviour

Related Issues

Fixes #855