feat(gemini-cli): add Google One login and improve auto-discovery

Add Google One personal account login to Gemini CLI OAuth flow:
- CLI --login shows mode menu (Code Assist vs Google One)
- Web management API accepts project_id=GOOGLE_ONE sentinel
- Auto-discover project via onboardUser without cloudaicompanionProject when project is unresolved

Improve robustness of auto-discovery and token handling:
- Add context-aware auto-discovery polling (30s timeout, 2s interval)
- Distinguish network errors from project-selection-required errors
- Refresh expired access tokens in readAuthFile before project lookup
- Extend project_id auto-fill to gemini auth type (was antigravity-only)

Unify credential file naming to geminicli- prefix for both CLI and web.

Add extractAccessToken unit tests (9 cases).

sdk/auth/filestore.go

@@ -4,8 +4,10 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"io/fs"
 	"net/http"
+	"net/url"
 	"os"
 	"path/filepath"
 	"strings"
@@ -186,15 +188,21 @@ func (s *FileTokenStore) readAuthFile(path, baseDir string) (*cliproxyauth.Auth,
 	if provider == "" {
 		provider = "unknown"
 	}
-	if provider == "antigravity" {
+	if provider == "antigravity" || provider == "gemini" {
 		projectID := ""
 		if pid, ok := metadata["project_id"].(string); ok {
 			projectID = strings.TrimSpace(pid)
 		}
 		if projectID == "" {
-			accessToken := ""
-			if token, ok := metadata["access_token"].(string); ok {
-				accessToken = strings.TrimSpace(token)
+			accessToken := extractAccessToken(metadata)
+			// For gemini type, the stored access_token is likely expired (~1h lifetime).
+			// Refresh it using the long-lived refresh_token before querying.
+			if provider == "gemini" {
+				if tokenMap, ok := metadata["token"].(map[string]any); ok {
+					if refreshed, errRefresh := refreshGeminiAccessToken(tokenMap, http.DefaultClient); errRefresh == nil {
+						accessToken = refreshed
+					}
+				}
 			}
 			if accessToken != "" {
 				fetchedProjectID, errFetch := FetchAntigravityProjectID(context.Background(), accessToken, http.DefaultClient)
@@ -304,6 +312,67 @@ func (s *FileTokenStore) baseDirSnapshot() string {
 	return s.baseDir
 }
 
+func extractAccessToken(metadata map[string]any) string {
+	if at, ok := metadata["access_token"].(string); ok {
+		if v := strings.TrimSpace(at); v != "" {
+			return v
+		}
+	}
+	if tokenMap, ok := metadata["token"].(map[string]any); ok {
+		if at, ok := tokenMap["access_token"].(string); ok {
+			if v := strings.TrimSpace(at); v != "" {
+				return v
+			}
+		}
+	}
+	return ""
+}
+
+func refreshGeminiAccessToken(tokenMap map[string]any, httpClient *http.Client) (string, error) {
+	refreshToken, _ := tokenMap["refresh_token"].(string)
+	clientID, _ := tokenMap["client_id"].(string)
+	clientSecret, _ := tokenMap["client_secret"].(string)
+	tokenURI, _ := tokenMap["token_uri"].(string)
+
+	if refreshToken == "" || clientID == "" || clientSecret == "" {
+		return "", fmt.Errorf("missing refresh credentials")
+	}
+	if tokenURI == "" {
+		tokenURI = "https://oauth2.googleapis.com/token"
+	}
+
+	data := url.Values{
+		"grant_type":    {"refresh_token"},
+		"refresh_token": {refreshToken},
+		"client_id":     {clientID},
+		"client_secret": {clientSecret},
+	}
+
+	resp, err := httpClient.PostForm(tokenURI, data)
+	if err != nil {
+		return "", fmt.Errorf("refresh request: %w", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	body, _ := io.ReadAll(resp.Body)
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("refresh failed: status %d", resp.StatusCode)
+	}
+
+	var result map[string]any
+	if errUnmarshal := json.Unmarshal(body, &result); errUnmarshal != nil {
+		return "", fmt.Errorf("decode refresh response: %w", errUnmarshal)
+	}
+
+	newAccessToken, _ := result["access_token"].(string)
+	if newAccessToken == "" {
+		return "", fmt.Errorf("no access_token in refresh response")
+	}
+
+	tokenMap["access_token"] = newAccessToken
+	return newAccessToken, nil
+}
+
 // jsonEqual compares two JSON blobs by parsing them into Go objects and deep comparing.
 func jsonEqual(a, b []byte) bool {
 	var objA any