Clarify field separator being a guess when importing csv (#3996)

* clarify that the initially selected field separator is a guess

* explain why the field seperator setting might be locked

ftl/core/importing.ftl

@@ -15,6 +15,7 @@ importing-colon = Colon
 importing-comma = Comma
 importing-empty-first-field = Empty first field: { $val }
 importing-field-separator = Field separator
+importing-field-separator-guessed =  Field separator (guessed)
 importing-field-mapping = Field mapping
 importing-field-of-file-is = Field <b>{ $val }</b> of file is:
 importing-fields-separated-by = Fields separated by: { $val }
@@ -217,6 +218,9 @@ importing-field-separator-help =
     Please note that if this character appears in any field itself, the field has to be
     quoted accordingly to the CSV standard. Spreadsheet programs like LibreOffice will
     do this automatically.
+
+    It cannot be changed if the text file forces use of a specific separator via a file header.
+    If a file header is not present, Anki will try to guess what the separator is.
 importing-allow-html-in-fields-help =
     Enable this if the file contains HTML formatting. E.g. if the file contains the string
     '&lt;br&gt;', it will appear as a line break on your card. On the other hand, with this

ts/routes/import-csv/FileOptions.svelte

@@ -65,7 +65,9 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
         <SettingTitle
             on:click={() => openHelpModal(Object.keys(settings).indexOf("delimiter"))}
         >
-            {settings.delimiter.title}
+            {$metadata.forceDelimiter
+                ? settings.delimiter.title
+                : tr.importingFieldSeparatorGuessed()}
         </SettingTitle>
     </EnumSelectorRow>