feat(rules): support multiline or |

treat lines ending with unquoted `|` or `&` as continued
conditions in `do` block headers so nested blocks parse correctly
across line breaks.

update `on` condition splitting to avoid breaking on newlines that
follow an unescaped trailing pipe, while still respecting quotes,
escapes, and bracket nesting.

add coverage for multiline `|`/`&` continuations in `do` parsing,
`splitAnd`, `parseOn`, and HTTP flow nested block behavior.

internal/route/rules/http_flow_block_test.go

@@ -456,7 +456,8 @@ func TestHTTPFlow_NestedBlocks_RemoteOverride(t *testing.T) {
 	err := parseRules(`
 header X-Test-Header {
   set header X-Remote-Type public
-  remote 127.0.0.1 | remote 192.168.0.0/16 {
+  remote 127.0.0.1 |
+	remote 192.168.0.0/16 {
     set header X-Remote-Type private
   }
 }