fix: add --no-verify support for parallel executor commits (#1116)

Parallel executor agents trigger pre-commit hooks on every commit, causing
build lock contention (e.g., cargo lock fights in Rust projects) and 40+
minute delays from cascading retries.

Changes:
- Add --no-verify flag to gsd-tools commit command (commands.cjs)
- Wire --no-verify through gsd-tools.cjs CLI parser
- Update execute-phase.md to instruct parallel agents to use --no-verify
- Add post-wave hook validation step so orchestrator runs hooks once
- Update execute-plan.md pre-commit handling: parallel agents skip hooks,
  sequential agents still handle hooks normally
- Add parallel agent note to git-integration.md reference

Fixes #1116

get-shit-done/references/git-integration.md

@@ -61,6 +61,10 @@ node "$HOME/.claude/get-shit-done/bin/gsd-tools.cjs" commit "docs: initialize [p
 
 Each task gets its own commit immediately after completion.
 
+> **Parallel agents:** When running as a parallel executor (spawned by execute-phase),
+> use `--no-verify` on all commits to avoid pre-commit hook lock contention.
+> The orchestrator validates hooks once after all agents complete.
+
 ```
 {type}({phase}-{plan}): {task-name}