fix: critical parity bugs - enable tools, default permissions, tool input

Tighten prompt-mode parity for the Rust CLI by enabling native tools in one-shot runs, defaulting fresh sessions to danger-full-access, and documenting the remaining TS-vs-Rust gaps.

The JSON prompt path now runs through the full conversation loop so tool use and tool results are preserved without streaming terminal noise, while the tool-input accumulator keeps the streaming {} placeholder fix without corrupting legitimate non-stream empty objects.

Constraint: Original TypeScript source was treated as read-only for parity analysis
Constraint: No new dependencies; keep the fix localized to the Rust port
Rejected: Leave JSON prompt mode on a direct non-tool API path | preserved the one-shot parity bug
Rejected: Keep workspace-write as the default permission mode | contradicted requested parity target
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep prompt text and prompt JSON paths on the same tool-capable runtime semantics unless upstream behavior proves they must diverge
Tested: cargo build --release; cargo test
Not-tested: live remote prompt run against LayoffLabs endpoint in this session

rust/crates/rusty-claude-cli/src/args.rs

@@ -12,7 +12,7 @@ pub struct Cli {
     #[arg(long, default_value = "claude-opus-4-6")]
     pub model: String,
 
-    #[arg(long, value_enum, default_value_t = PermissionMode::WorkspaceWrite)]
+    #[arg(long, value_enum, default_value_t = PermissionMode::DangerFullAccess)]
     pub permission_mode: PermissionMode,
 
     #[arg(long)]
@@ -99,4 +99,10 @@ mod tests {
         let logout = Cli::parse_from(["rusty-claude-cli", "logout"]);
         assert_eq!(logout.command, Some(Command::Logout));
     }
+
+    #[test]
+    fn defaults_to_danger_full_access_permission_mode() {
+        let cli = Cli::parse_from(["rusty-claude-cli"]);
+        assert_eq!(cli.permission_mode, PermissionMode::DangerFullAccess);
+    }
 }