fix: use forwarded attribute lookups for SafeTextIO

[jeffersonngu]

No description provided.

[cursor]

PR Summary

Low Risk
Small transparency fix around attribute delegation; write/censoring path is unchanged.

Overview
SafeTextIO now delegates non-write attribute access to the underlying stream, so callers see real stream behavior (e.g. encoding, fileno) instead of empty typing.TextIO stubs.

The wrapper stores the original TextIO in __wrapped and implements __getattribute__ to resolve most names on that object while keeping write (and dunder lookups) on the wrapper for secret censoring. Class docstring explains why inheritance from TextIO alone is insufficient at runtime.

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