Preserve resumed session command exhaustiveness

Resolve an overlap introduced while adding G010 session command UX so resumed /session handling remains exhaustive without an unreachable fallback arm.\n\nConstraint: G010 leader verification found rusty-claude-cli failed to compile because SlashCommand::Session was both handled and still listed in the unsupported command union.\nRejected: leaving worker lanes to rediscover the compile failure | leader had direct verification evidence and a one-line localized fix.\nConfidence: high\nScope-risk: narrow\nDirective: Keep resumed /session subcommands routed through run_resumed_session_command; do not re-add Session to the unsupported slash-command union.\nTested: cargo fmt --manifest-path rust/Cargo.toml --all -- --check; cargo test --manifest-path rust/Cargo.toml -p rusty-claude-cli --test resume_slash_commands -- --nocapture; cargo test --manifest-path rust/Cargo.toml -p rusty-claude-cli --test compact_output -- --nocapture; git diff --check\nNot-tested: full cargo test --workspace not rerun for this one-line compile fix; G010 leader verification continues separately.

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

@@ -4147,7 +4147,6 @@ fn run_resume_command(
         | SlashCommand::Fast
         | SlashCommand::Exit
         | SlashCommand::Summary
-        | SlashCommand::Session { .. }
         | SlashCommand::Desktop
         | SlashCommand::Brief
         | SlashCommand::Advisor