v2.1.3 — Agent management hardening and CI fix

Fixes

• Fix agent_advanced.bulk_delete pagination to use SDK cursor-based paging
• Fix agent_advanced.get_config to propagate tool-list failures instead of returning misleading empty tools
• Apply rustfmt formatting to agent_advanced management so stable/nightly CI formatting gates pass

Validation

• cargo fmt --all -- --check
• cargo check
• cargo clippy -p letta-server -p letta-types --all-targets --no-deps -- -D warnings
• cargo test -p letta-server
• cargo test -p letta

Notes

• Message-side search_memory remains correct but client-side for now; safe server-side replacement is tracked separately because current Letta API search is org-wide and not safely agent-scoped.
• Follow-up tracker: bd-2kl