docs: carry the business rules the API reference states

[edu-stark]

Summary

• Adjudicated docs/SDK docstring drift for starkbank/sdk-python: carries the winning business-rule text (per DECISIONS.md §6, backed by PLAN.md §2.1 where undisputed) into docstrings across 20 resource families, since agent tooling and IDE tooltips read the installed package's docstrings, not the docs site.
• Fixes one README.md sample (CorporateWithdrawal) that passed a description kwarg no constructor accepts.
• Comment/docstring lines only — no behavior changes; verified via a tokenize-based checker that every changed line in every touched .py file falls inside a docstring or comment span.

Resource families touched: invoice, invoice-pull-subscription, transfer, boleto, boleto-payment, merchant-card (+ Log), merchant-installment (+ Log), merchant-purchase (+ Log), merchant-session (+ Log), brcode-payment, dynamic-brcode, event, webhook, deposit, transaction, workspace, payment-request, darf-payment, tax-payment, utility-payment, dict-key, split-profile.

Post-review fixes applied on this branch (amended into the single commit):

• starkbank/transaction/__transaction.py: removed an unadjudicated "use starkbank.transfer.create instead" recommendation from the deprecated create() docstring (Transfer is not an equivalent replacement for internal inter-workspace transactions); replaced with wording grounded in the actual deprecation behavior.
• starkbank/splitprofile/__splitprofile.py: removed the undocumented receiver_ids parameter bullet from page()'s docstring per DECISIONS §6 L-033 (text-only; the kwarg itself is unchanged, still silently forwarded and unsupported by the API — a separate code-level cleanup, not in scope here).

Test plan

• python3 -m compileall -q on all 26 changed .py files — exit 0
• Tokenize-based diff checker confirms every changed line (old and new) across all 26 files falls inside a docstring/comment token span
• No trailing whitespace introduced on any added line
• git status --short clean; branch exactly 1 commit ahead of master
• CHANGELOG.md entry added (repo has precedent: identical "### Fixed / - Docstrings" entries at v0.2.0 and v0.2.1)

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