Clean up documentation drift

[wilsonfreitas]

Context

Several docs examples and claims drift from current behavior. Examples include async client shutdown, currency async examples, date input support, regional economy modes, and TaxaJuros URL/version references.

Scope

Review README, Sphinx docs, and examples for accuracy against current code behavior and supported public APIs.

Branching

Create the implementation branch from project-health-hardening and merge the fix back into project-health-hardening before any merge to main.

Acceptance Criteria

• README, docs, and examples match current behavior.
• The async client shutdown example is corrected.
• Date input and regional economy mode documentation match implementation.
• Docs build instructions are verified or updated if dependencies are missing.

[wilsonfreitas]

Completed via #55 and merged into project-health-hardening.