fix: use npm ci in bootstrap to prevent dirty lockfile blocking merges

setup.sh ran npm install which modified package-lock.json, causing
git merge to refuse during channel skill installation. Switch to
npm ci (deterministic, doesn't modify lockfile) and clean up stale
peer flags in the lockfile.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/setup/SKILL.md

@@ -58,7 +58,7 @@ Run `bash setup.sh` and parse the status block.
   - macOS: `brew install node@22` (if brew available) or install nvm then `nvm install 22`
   - Linux: `curl -fsSL https://deb.nodesource.com/setup_22.x | sudo -E bash - && sudo apt-get install -y nodejs`, or nvm
   - After installing Node, re-run `bash setup.sh`
-- If DEPS_OK=false → Read `logs/setup.log`. Try: delete `node_modules` and `package-lock.json`, re-run `bash setup.sh`. If native module build fails, install build tools (`xcode-select --install` on macOS, `build-essential` on Linux), then retry.
+- If DEPS_OK=false → Read `logs/setup.log`. Try: delete `node_modules`, re-run `bash setup.sh`. If native module build fails, install build tools (`xcode-select --install` on macOS, `build-essential` on Linux), then retry.
 - If NATIVE_OK=false → better-sqlite3 failed to load. Install build tools and re-run.
 - Record PLATFORM and IS_WSL for later steps.