Add pre-commit hook installation to onboarding and upgrade processes

- prompts/onboarding.md: Step 2c installs git pre-commit hook for new projects
- scripts/upgrade.sh: Installs pre-commit hook during upgrade (with symlink detection)
- scripts/install.sh: Mentions hook installation in post-install next steps

tasks/hook-install-process/.state

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+implement

tasks/hook-install-process/.state.approvals

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+research:approved|2026-06-15T18:20:49.509508+00:00|user

tasks/hook-install-process/SPEC.md

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+# Hook Installation in Onboarding and Upgrade
+
+## Goal
+Add pre-commit hook installation to both the new-project onboarding process and the existing-project upgrade process, so enforcement is set up automatically.
+
+## Requirements
+- Onboarding prompt includes a step to install the git pre-commit hook
+- upgrade.sh installs the hook during upgrade (with symlink detection)
+- install.sh mentions hook installation in post-install next steps
+
+## Acceptance Criteria
+- [x] prompts/onboarding.md includes Step 2c for hook installation
+- [x] scripts/upgrade.sh installs hook and detects existing hooks
+- [x] scripts/install.sh mentions hook installation
+- [x] Shell scripts pass syntax check
+- [x] All 200 tests pass