Keep CLI parity features local and controllable

The remaining slash commands already existed in the REPL path, so this change
focuses on wiring the active CLI parser and runtime to expose them safely.
`--version` now exits through a local reporting path, and `--allowedTools`
constrains both advertised and executable tools without changing the underlying
command surface.

Constraint: The active CLI parser lives in main.rs, so a full parser unification would be broader than requested
Constraint: --version must not require API credentials or construct the API client
Rejected: Migrate the binary to the clap parser in args.rs | too large for a parity patch
Rejected: Enforce allowed tools only at request construction time | execution-time mismatch risk
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep local-only flags like --version on pre-runtime codepaths and mirror tool allowlists in both definition and execution paths
Tested: cargo fmt; cargo clippy --workspace --all-targets -- -D warnings; cargo test; cargo run -q -p rusty-claude-cli -- --version; cargo run -q -p rusty-claude-cli -- --help
Not-tested: Interactive live API conversation with restricted tool allowlists

rust/README.md

@@ -132,7 +132,9 @@ cargo run -p rusty-claude-cli -- --resume session.json /memory /config
 - `bootstrap-plan` — print the current bootstrap skeleton
 - `system-prompt [--cwd PATH] [--date YYYY-MM-DD]` — render the synthesized system prompt
 - `--help` / `-h` — show CLI help
-- `--version` / `-V` — print the CLI version
+- `--version` / `-V` — print the CLI version and build info locally (no API call)
+- `--output-format text|json` — choose non-interactive prompt output rendering
+- `--allowedTools <tool[,tool...]>` — restrict enabled tools for interactive sessions and prompt-mode tool use
 
 ### Interactive slash commands