fix(narrow): hashlib 摘要写字节改用 uint8(...)

sha256/sha1/md5 的 digest 阶段把 32/64 位掩码结果写入 bytes 元素（i8），触发隐式窄化；统一加 uint8(...)（与 __sha512 一致）

hashlib/__md5.vp

@@ -118,11 +118,11 @@ class md5:
         # Write total bit count
         bits: uint64 = self.count << 3
         for i in range(8):
-            self.buf[MD5_BLOCK_LEN - 8 + i] = (bits >> (i * 8)) & 0xFF
+            self.buf[MD5_BLOCK_LEN - 8 + i] = uint8((bits >> (i * 8)) & 0xFF)
         self.transform(self.buf)
         # State registers to little-endian byte output output
         for i in range(4):
-            out[i * 4 + 0] = (self.state[i] >>  0) & 0xFF
-            out[i * 4 + 1] = (self.state[i] >>  8) & 0xFF
-            out[i * 4 + 2] = (self.state[i] >> 16) & 0xFF
-            out[i * 4 + 3] = (self.state[i] >> 24) & 0xFF
+            out[i * 4 + 0] = uint8((self.state[i] >>  0) & 0xFF)
+            out[i * 4 + 1] = uint8((self.state[i] >>  8) & 0xFF)
+            out[i * 4 + 2] = uint8((self.state[i] >> 16) & 0xFF)
+            out[i * 4 + 3] = uint8((self.state[i] >> 24) & 0xFF)

hashlib/__sha1.vp

@@ -105,11 +105,11 @@ class sha1:
         bits: uint64 = self.count << 3
         # SHA1 big-endian write length
         for i in range(8):
-            self.buf[SHA1_BLOCK_LEN - 8 + i] = (bits >> (56 - i * 8)) & 0xFF
+            self.buf[SHA1_BLOCK_LEN - 8 + i] = uint8((bits >> (56 - i * 8)) & 0xFF)
         self.transform(self.buf)
         # State registers to big-endian byte output output output
         for i in range(5):
-            out[i * 4 + 0] = (self.state[i] >> 24) & 0xFF
-            out[i * 4 + 1] = (self.state[i] >> 16) & 0xFF
-            out[i * 4 + 2] = (self.state[i] >>  8) & 0xFF
-            out[i * 4 + 3] = (self.state[i] >>  0) & 0xFF
+            out[i * 4 + 0] = uint8((self.state[i] >> 24) & 0xFF)
+            out[i * 4 + 1] = uint8((self.state[i] >> 16) & 0xFF)
+            out[i * 4 + 2] = uint8((self.state[i] >>  8) & 0xFF)
+            out[i * 4 + 3] = uint8((self.state[i] >>  0) & 0xFF)

hashlib/__sha256.vp

@@ -108,11 +108,11 @@ class sha256:
         string.memset(self.buf + idx, 0, SHA256_BLOCK_LEN - 8 - idx)
         bits: uint64 = self.count << 3
         for i in range(8):
-            self.buf[SHA256_BLOCK_LEN-8+i] = (bits >> (56 - i*8)) & 0xFF
+            self.buf[SHA256_BLOCK_LEN-8+i] = uint8((bits >> (56 - i*8)) & 0xFF)
         self.transform(self.buf)
         # Byte order 32-bit words
         for i in range(8):
-            out[i * 4 + 0] = (self.state[i] >> 24) & 0xFF
-            out[i * 4 + 1] = (self.state[i] >> 16) & 0xFF
-            out[i * 4 + 2] = (self.state[i] >>  8) & 0xFF
-            out[i * 4 + 3] = (self.state[i] >>  0) & 0xFF
+            out[i * 4 + 0] = uint8((self.state[i] >> 24) & 0xFF)
+            out[i * 4 + 1] = uint8((self.state[i] >> 16) & 0xFF)
+            out[i * 4 + 2] = uint8((self.state[i] >>  8) & 0xFF)
+            out[i * 4 + 3] = uint8((self.state[i] >>  0) & 0xFF)