feat(skills): add AGY — Google Gemini CLI second-opinion router

Sibling of the grok skill: routes text/verify/review (+ review-files,
review-diff, raw) to the official Google Gemini CLI (gemini, npm global,
v0.45.1) for an independent second model. ask-gemini.sh mirrors ask-grok.sh
(identity-aware gating, binary auto-locate, cygpath hardening, prompt-file
inputs, clean stdout/stderr separation, JSON .response extraction). review
modes copy targets into a temp dir + --include-directories to bypass
Gemini's gitignore/workspace sandbox. verify/review pinned to
gemini-3.1-pro-preview (GEMINI_MODEL overridable). migrate-identity.sh
auto-detects gemini and writes a per-machine identity.json gemini block.
Auth: Google OAuth (no key). Fleet Gemini host: GURU-5070.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/scripts/migrate-identity.sh

@@ -96,6 +96,28 @@ else
     echo "  Grok: not installed"
 fi
 
+# Detect Google Gemini CLI — optional capability extension (independent second
+# model: verify / review / text). Sibling of Grok. Per-machine; sets identity
+# gemini.installed so the /agy skill knows whether it can run locally. Does NOT
+# set is_fleet_host (manual fleet-coordination choice, preserved if present).
+GEMINI_BIN=""
+if command -v gemini >/dev/null 2>&1; then
+    GEMINI_BIN="$(command -v gemini)"
+else
+    for c in "${APPDATA:-}/npm/gemini" "$HOME/AppData/Roaming/npm/gemini" \
+             "/usr/local/bin/gemini" "$HOME/.npm-global/bin/gemini"; do
+        if [ -n "$c" ] && [ -x "$c" ]; then GEMINI_BIN="$c"; break; fi
+    done
+fi
+if [ -n "$GEMINI_BIN" ]; then
+    GEMINI_BIN="$(cygpath -m "$GEMINI_BIN" 2>/dev/null || echo "$GEMINI_BIN")"
+    GEMINI_INSTALLED="true"
+    echo "  Gemini: installed ($GEMINI_BIN)"
+else
+    GEMINI_INSTALLED="false"
+    echo "  Gemini: not installed"
+fi
+
 # Build updated identity.json
 echo ""
 echo "[INFO] Updating identity.json..."
@@ -136,6 +158,17 @@ else:
     g['installed'] = False
 data['grok'] = g
 
+# Gemini capability flag (per-machine, sibling of grok). Preserve manual is_fleet_host.
+gm = data.get('gemini') or {}
+if '$GEMINI_INSTALLED' == 'true':
+    gm['installed'] = True
+    gm['binary'] = r'$GEMINI_BIN'
+    gm.setdefault('auth', 'oauth')
+    gm.setdefault('capabilities', ['text', 'verify', 'review'])
+else:
+    gm['installed'] = False
+data['gemini'] = gm
+
 # Coord API endpoint — populate only if absent so existing machines keep their override.
 if 'coord_api' not in data:
     data['coord_api'] = '$COORD_API_DEFAULT'
@@ -158,6 +191,7 @@ echo "  ollama.prose_model: $PROSE_MODEL"
 echo "  platform: $PLATFORM"
 echo "  architecture: $ARCH"
 echo "  grok.installed: $GROK_INSTALLED"
+echo "  gemini.installed: $GEMINI_INSTALLED"
 echo "  coord_api: (default $COORD_API_DEFAULT if not already set)"
 echo ""
 echo "Review: cat $IDENTITY_PATH"