feat(execute-phase): support wave-specific execution

commands/gsd/execute-phase.md

@@ -1,7 +1,7 @@
 ---
 name: gsd:execute-phase
 description: Execute all plans in a phase with wave-based parallelization
-argument-hint: "<phase-number> [--gaps-only]"
+argument-hint: "<phase-number> [--wave N] [--gaps-only]"
 allowed-tools:
   - Read
   - Write
@@ -18,6 +18,10 @@ Execute all plans in a phase using wave-based parallel execution.
 
 Orchestrator stays lean: discover plans, analyze dependencies, group into waves, spawn subagents, collect results. Each subagent loads the full execute-plan context and handles its own plan.
 
+Optional wave filter:
+- `--wave N` executes only Wave `N` for pacing, quota management, or staged rollout
+- phase verification/completion still only happens when no incomplete plans remain after the selected wave finishes
+
 Context budget: ~15% orchestrator, 100% fresh per subagent.
 </objective>
 
@@ -30,6 +34,7 @@ Context budget: ~15% orchestrator, 100% fresh per subagent.
 Phase: $ARGUMENTS
 
 **Flags:**
+- `--wave N` — Execute only Wave `N` in the phase. Use when you want to pace execution or stay inside usage limits.
 - `--gaps-only` — Execute only gap closure plans (plans with `gap_closure: true` in frontmatter). Use after verify-work creates fix plans.
 
 Context files are resolved inside the workflow via `gsd-tools init execute-phase` and per-subagent `<files_to_read>` blocks.