Tolerate redundant cwd prefixes in SmartTool paths

[Zorlin]

Summary

• Add a shared SmartTool path resolver for local file arguments
• Keep absolute paths unchanged
• Recover when a relative path repeats the current cwd basename, e.g. cwd is .../codex-rs and the model passes codex-rs/sandboxing/mod.rs
• Apply the resolver to both SmartRead and SmartWrite while preserving outside-project validation

Testing

• just test -p codex-core smart_path smart_read smart_write
• just fix -p codex-core
• just fmt
• cargo build --release -p codex-cli

Local install

• Installed /home/wings/projects/rolodex/codex-rs/target/release/rolodex to /usr/local/bin/rolodex