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.

.omx/ultragoal/get-goal-G010-session-hygiene.active-20260515T020953Z.json

@@ -0,0 +1 @@
+{"goal":{"threadId":"019e2560-a38d-7282-bb33-58c944cdcbc9","objective":"Complete the approved Claw Code 2.0 ultragoal delivery: implement all classified ROADMAP.md backlog work through execution-sized stream goals G001-G012, using .omx/ultragoal/ledger.jsonl as the durable audit trail and .omx/plans/claw-code-2-0-adaptive-plan.md as the source plan.","status":"active","tokensUsed":4771357,"timeUsedSeconds":14733,"createdAt":1778745278,"updatedAt":1778810966},"remainingTokens":null,"completionBudgetReport":null}