Follow pagination cursors when vMCP queries backends

[JAORMX]

Part of #5743 (Workstream B: 2025-11-25 compliance).

Gap

vMCP queries backends with single tools/list / resources/list / prompts/list calls and never follows nextCursor (pkg/vmcp/client/client.go, queryTools/queryResources/queryPrompts). Backends that paginate get silently truncated after page 1 — missing tools with no error.

This got more urgent with the go-sdk migration: go-sdk-based servers paginate tools/list at 1000 by default, so truncation now happens against our own servers too.

Proposed work

• Loop on nextCursor in all three query paths until exhausted (with a sane upper bound to protect against misbehaving backends).
• Add a test with a paginating fake backend.

Priority: High — correctness bug.

[JAORMX]

Closing as completed — this was implemented but the issue was never auto-closed (the PR used Refs, not Closes).

Implemented by #5851 ("Follow list pagination cursors in vMCP capability discovery", commit cab6e171), later extended by #5875.

The fix does exactly what this issue asked:

• A generic pagination.ListAll helper (pkg/vmcp/internal/pagination/pagination.go) follows nextCursor to exhaustion, with the requested safety bound (repeated-cursor abort + a maxIterations cap).
• All three query paths now loop cursors — queryTools / queryResources / queryPrompts (plus queryResourceTemplates) in pkg/vmcp/client/client.go, and the per-session connector in pkg/vmcp/session/internal/backend/mcp_session.go.
• A paginating fake-backend test was added (test/integration/vmcp/pagination_regression_test.go, un-skipped and strengthened to assert the full 1100-tool set with distinct names + last-tool routing), plus unit tests for pagination.ListAll and the per-session path.

Verified present on main.