[codex] add sanitize_display terminal injection tests

[leemeo3]

Summary

• Add focused unit coverage for sanitize_display against CSI and OSC terminal escape sequences.
• Cover carriage returns, backspaces, and C0/C1 control characters used for terminal injection or line overwrite attempts.
• Keep the existing benign passthrough assertion so the tests guard against over-sanitizing.

Fixes #212

Testing

• cargo test sanitize
• cargo clippy --all-targets --all-features -- -D warnings
• cargo build --all-targets
• cargo test

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