docs: README CLI-support + CONTRIBUTING reflect ./aipass install flow

- README: setup.sh mention tied to the ./aipass install command + notes hook merge-not-overwrite
- CONTRIBUTING: contributor bootstrap is ./aipass install --no-init (no first-project scaffold in the engine repo)

CONTRIBUTING.md

@@ -15,7 +15,7 @@ PRs are welcome after an issue has been discussed. Keep changes focused -- one f
 - Python 3.10+
 - Tests: `pytest` (4,900+ tests across the project)
 - Quality: AIPass uses its own standards system ([seedgo](src/aipass/seedgo/README.md)) for automated audits
-- Run `./setup.sh` to bootstrap the full environment
+- Run `./aipass install --no-init` to bootstrap the full environment (contributors work in the engine repo itself — no first-project scaffold needed)
 
 ## Questions?
 

README.md

@@ -232,7 +232,7 @@ AIPass is built and tested with **Claude Code** on Linux/WSL.
 | [Claude Code](https://code.claude.com/docs) | `claude -p "prompt" --permission-mode bypassPermissions` | Fully tested |
 | [Codex](https://github.com/openai/codex) | `codex exec "prompt" --dangerously-bypass-approvals-and-sandbox` | Experimental |
 
-setup.sh auto-detects which CLIs are installed and configures hooks for each.
+The installer (`./aipass install`, powered by setup.sh) auto-detects which CLIs are installed and configures hooks for each — merging with any hooks you've already wired, never overwriting them.
 
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