fix(tools): page through MCP tools/list nextCursor

[icn5381]

Summary

connect_mcp_servers called list_tools() once and registered only the tools on the first page. A server that paginates tool discovery (returns a nextCursor) silently exposed a partial tool surface: every tool past the first page was omitted with no error.

Follow nextCursor page to page until the server stops returning one, then register the full set. Track seen cursors so a misbehaving server that re-issues the same cursor cannot trap discovery in a loop.

The paging loop lives in a new _collect_tools helper so it is unit-testable without standing up a transport/registry.

Type

• Fix

Verification

• Relevant tests pass locally: uv run pytest tests/test_mcp_tools_pagination.py -v -> 3 passed
• Relevant lint / type checks pass locally: uv run ruff format (2 files unchanged), uv run ruff check (all passed)
• User-facing docs or screenshots updated: N/A (internal discovery fix)

Risk

• Security impact considered: no new code path beyond iterating a cursor the server already returns; no shell, no network egress change
• Backward compatibility considered: single-page servers (no nextCursor) hit the same one-iteration path as before
• Rollback path is clear: revert restores the single list_tools() call

Related Issues

Fixes #301