Line numbers are places in import and export; fix stale scripts

Import: each row's place is its line number, so blank lines leave a
place empty; a fully numbered text file ("38. Title") or a Rank column
gives places directly, and repeated numbers take the next free place.
Entries are added at those places (existing ones there move down), the
review shows each row's #, and the room check covers the highest place.

Export writes a blank line for every empty place, so line N is #N and a
file round-trips.

Static files now carry an ETag and unversioned ones are revalidated on
every load. Scripts import each other without a ?v= tag, so browsers kept
an hour-old import.js (with the "null" bug) after an update.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/importer/importer_test.go

@@ -1,6 +1,7 @@
 package importer
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
 
@@ -8,17 +9,28 @@ import (
 )
 
 func TestParseText(t *testing.T) {
-	got, err := Parse([]byte("1. Heat (1995)\n2) 2001: A Space Odyssey\n\n3 - Alien [1979]\n"), "list.txt")
+	got, err := Parse([]byte("1. Heat (1995)\n2) 2001: A Space Odyssey\n\n4 - Alien [1979]\n"), "list.txt")
 	if err != nil {
 		t.Fatal(err)
 	}
-	want := []Row{{Title: "Heat", Year: "1995"}, {Title: "2001: A Space Odyssey"}, {Title: "Alien", Year: "1979"}}
+	want := []Row{{Place: 1, Title: "Heat", Year: "1995"}, {Place: 2, Title: "2001: A Space Odyssey"}, {Place: 4, Title: "Alien", Year: "1979"}}
 	if !reflect.DeepEqual(got, want) {
 		t.Fatalf("got %+v", got)
 	}
-	// Not every line is numbered, so nothing is stripped.
-	got, _ = Parse([]byte("2001: A Space Odyssey\nHeat\n1917\n"), "x.txt")
-	if got[0].Title != "2001: A Space Odyssey" || got[2].Title != "1917" {
+	// Not every line is numbered, so nothing is stripped; line numbers are
+	// the places, and a blank line leaves one empty.
+	got, _ = Parse([]byte("2001: A Space Odyssey\nHeat\n\n1917\n"), "x.txt")
+	if got[0].Title != "2001: A Space Odyssey" || got[2].Title != "1917" || got[2].Place != 4 {
+		t.Fatalf("got %+v", got)
+	}
+	// Numbers win over line numbers when every line has one.
+	got, _ = Parse([]byte("1. Super Mario Sunshine\n38. Super Mario World\n"), "games.txt")
+	if got[0].Place != 1 || got[1].Place != 38 || got[1].Title != "Super Mario World" {
+		t.Fatalf("got %+v", got)
+	}
+	// A repeated number takes the next free place, keeping the file's order.
+	got, _ = Parse([]byte("3. A\n3. B\n1. C\n"), "x.txt")
+	if fmt.Sprint(got) != fmt.Sprint([]Row{{Place: 1, Title: "C"}, {Place: 3, Title: "A"}, {Place: 4, Title: "B"}}) {
 		t.Fatalf("got %+v", got)
 	}
 }
@@ -30,20 +42,26 @@ func TestParseCSV(t *testing.T) {
 		t.Fatal(err)
 	}
 	want := []Row{
-		{Title: "Heat", Year: "1995", Subtitle: "Michael Mann"},
-		{Title: "Alien", Year: "1979", Subtitle: "Ridley Scott", Note: "Tense, perfect"},
+		{Place: 1, Title: "Heat", Year: "1995", Subtitle: "Michael Mann"},
+		{Place: 2, Title: "Alien", Year: "1979", Subtitle: "Ridley Scott", Note: "Tense, perfect"},
 	}
 	if !reflect.DeepEqual(got, want) {
 		t.Fatalf("got %+v", got)
 	}
-	// Canon's own export: one quoted column, no header.
-	got, _ = Parse([]byte("\xef\xbb\xbf\"Heat\"\r\n\"Crouching Tiger, Hidden Dragon\"\r\n"), "films.csv")
-	if len(got) != 2 || got[1].Title != "Crouching Tiger, Hidden Dragon" {
+	// Canon's own export: one column, no header, a blank line for an empty
+	// place.
+	got, _ = Parse([]byte("\xef\xbb\xbfHeat\r\n\r\n\"Crouching Tiger, Hidden Dragon\"\r\n"), "films.csv")
+	if len(got) != 2 || got[1].Title != "Crouching Tiger, Hidden Dragon" || got[1].Place != 3 {
+		t.Fatalf("got %+v", got)
+	}
+	// With a header, the first row after it is #1.
+	got, _ = Parse([]byte("Title\nHeat\n\nAlien\n"), "x.csv")
+	if got[0].Place != 1 || got[1].Place != 3 {
 		t.Fatalf("got %+v", got)
 	}
 	// Headerless rank,title,year.
-	got, _ = Parse([]byte("1,Heat,1995\n2,Alien,1979\n"), "x.csv")
-	if got[1] != (Row{Title: "Alien", Year: "1979"}) {
+	got, _ = Parse([]byte("1,Heat,1995\n5,Alien,1979\n"), "x.csv")
+	if got[1] != (Row{Place: 5, Title: "Alien", Year: "1979"}) {
 		t.Fatalf("got %+v", got)
 	}
 	if _, err := Parse([]byte("\n \n"), "x.txt"); err != ErrEmpty {