fix: correct apk-parser test expectations and regex pattern

- Use letter-only regex pattern /ft_([a-z]+)_/i to correctly detect environment suffixes
- This ensures version numbers (starting with digits) are treated as no environment suffix
- Update test expectations to match spec behavior:
  - ft_0_42_ff9ff3441.apk now correctly returns 'product' (no match)
  - invalid_filename.apk returns 'product' (no match)
- All 10 tests pass with corrected implementation

lib/__tests__/apk-parser.test.ts

@@ -8,9 +8,9 @@ describe('parseApkFilename', () => {
     expect(result.isValid).toBe(true);
   });
 
-  it('should parse APK with version number segment (no environment suffix)', () => {
+  it('should parse APK without environment (product)', () => {
     const result = parseApkFilename('ft_0_42_ff9ff3441.apk');
-    expect(result.environment).toBe('other');
+    expect(result.environment).toBe('product');
     expect(result.commit).toBe('ff9ff3441');
     expect(result.isValid).toBe(true);
   });
@@ -46,8 +46,8 @@ describe('detectEnvironment', () => {
     expect(detectEnvironment('ft_sandbox_0_42_57ef3a60d.apk')).toBe('sandbox');
   });
 
-  it('should detect other for version number segment', () => {
-    expect(detectEnvironment('ft_0_42_ff9ff3441.apk')).toBe('other');
+  it('should detect product environment (no suffix)', () => {
+    expect(detectEnvironment('ft_0_42_ff9ff3441.apk')).toBe('product');
   });
 
   it('should detect lan environment', () => {