docs: Add inline examples to public API documentation

[josedab]

Description

Several public API functions in src/ modules are missing doc examples (/// # Examples blocks).

Task

• Pick 3-5 public functions that lack examples
• Add idiomatic /// # Examples blocks with rust,no_run code fences
• Run cargo doc --open to verify rendering

Helpful Context

• See existing examples in src/config.rs for the pattern
• Rust doc examples guide