[codex] fix CLI help for dynamic tool command

[ScriptedAlchemy]

What changed

• Handles tracedecay tool --help and tracedecay tool -h before dynamic tool dispatch so command-level help exits successfully.
• Keeps per-tool schema help working for commands like tracedecay tool search --help.
• Adds binary-level regression tests for top-level and representative nested subcommand help.
• Adds recursive parser coverage so visible clap subcommands continue to return DisplayHelp for --help.

Why

tool disables clap's built-in help flag so --help can be forwarded to dynamic MCP tool schemas. That made tracedecay tool --help error at the command boundary instead of printing help.

Impact

Users can now ask for help at the tool command level consistently with the rest of the CLI, while dynamic per-tool help remains intact.

Validation

• cargo fmt --check
• cargo test -q --test cli_help_test
• cargo test -q --bin tracedecay parse_tests
• cargo run -q -- tool --help

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Latest commit: 4cfebce

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Use OsString for argv pre-parsing

This switches every invocation through std::env::args(), which panics on Unix as soon as any argv item is not valid UTF-8. Previously Cli::parse() let clap read args_os() and reject/parse arguments through its normal error path; now commands that accept paths or pass-through tool values can abort before reaching clap even when they are unrelated to tool --help. Keep the help precheck on args_os()/OsStr and pass those values into clap instead of collecting Strings up front.

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