chore: install superpowers skill framework

- Add all 12 skills to .claude/skills/
- Add hooks for session-start bootstrap
- Add CLAUDE.md with using-superpowers bootstrap
- Configure settings.json with SessionStart hooks

.claude/skills/using-superpowers/references/codex-tools.md

@@ -0,0 +1,39 @@
+## Subagent dispatch requires multi-agent support
+
+Add to your Codex config (`~/.codex/config.toml`):
+
+```toml
+[features]
+multi_agent = true
+```
+
+This enables `spawn_agent`, `wait_agent`, and `close_agent` for skills like `dispatching-parallel-agents` and `subagent-driven-development`. When using subagent-driven-development, close reviewer subagents when their review returns. Keep each implementer subagent open until its task's review passes — the fix loop resumes the implementer — then close it. If your harness cannot send another message to a spawned agent, dispatch each fix round as a fresh implementer carrying the brief, the report file, and the findings.
+
+## Environment Detection
+
+Skills that create worktrees or finish branches should detect their
+environment with read-only git commands before proceeding:
+
+```bash
+GIT_DIR=$(cd "$(git rev-parse --git-dir)" 2>/dev/null && pwd -P)
+GIT_COMMON=$(cd "$(git rev-parse --git-common-dir)" 2>/dev/null && pwd -P)
+BRANCH=$(git branch --show-current)
+```
+
+- `GIT_DIR != GIT_COMMON` → already in a linked worktree (skip creation)
+- `BRANCH` empty → detached HEAD (cannot branch/push/PR from sandbox)
+
+See `using-git-worktrees` Step 0 and `finishing-a-development-branch`
+Step 1 for how each skill uses these signals.
+
+## Codex App Finishing
+
+When the sandbox blocks branch/push operations (detached HEAD in an
+externally managed worktree), the agent commits all work and informs
+the user to use the App's native controls:
+
+- **"Create branch"** — names the branch, then commit/push/PR via App UI
+- **"Hand off to local"** — transfers work to the user's local checkout
+
+The agent can still run tests, stage files, and output suggested branch
+names, commit messages, and PR descriptions for the user to copy.