fix(ci): drop node from brew install — unused, triggers gemini-cli rebuild

Run failed at 'brew install xcodegen node' AFTER both formulae upgraded
successfully under ARM: brew's 'installed dependents check' then tried to
rebuild gemini-cli (0.40.1 -> 0.46.0, an unrelated dev tool on the runner
that depends on node) and exited 1.

Verified node is NOT used by any step in pr-iphone-deploy.yml — only
xcodegen is. The only node references in the repo are in
scripts/prepare-release.cjs and scripts/verify-admin-web-docker.sh,
neither of which runs in this workflow. Node was a historical leftover.

Drop node from the brew install. No node upgrade = no dependents check =
no gemini-cli rebuild. Also sync AGENTS.md §5 step 4.

.github/workflows/pr-iphone-deploy.yml

@@ -82,12 +82,16 @@ jobs:
 
           echo "✅ Caches nettoyés (SPM cache préservé)"
 
-      - name: Install tools (xcodegen, node)
+      - name: Install tools (xcodegen)
         run: |
           # The act_runner shell can land under Rosetta 2 on Apple Silicon;
           # Homebrew lives in /opt/homebrew (ARM prefix), so run brew natively.
           # (Brew refuses to install/upgrade under Rosetta in the ARM prefix.)
-          arch -arm64 brew install xcodegen node
+          # Only xcodegen is needed — node is NOT used by any step in this
+          # workflow, and installing it triggers brew's "installed dependents
+          # check" which tries to rebuild unrelated formulae (e.g. gemini-cli)
+          # and fails the build.
+          arch -arm64 brew install xcodegen
 
       - name: Write Secrets.xcconfig from Gitea secrets
         env: