Add explicit get_by_id() and get_by_name() helpers for containers

[Flerpharos]

Summary
Add explicit container lookup helpers so callers do not have to discover slice-based indexing first.

Scope

• add get_by_id(...) and get_by_name(...) helpers
• keep existing indexing behavior compatible unless intentionally deprecated later
• update docs and examples to prefer the explicit read path

Acceptance criteria

• explicit lookup helpers exist on the relevant container types
• docs show the helper methods as the primary lookup path
• existing indexing behavior remains usable