M2: two Indexed resources are cached apart, and a stroke colour in a recovered Indexed space is reported (ISO 32000-2 8.6.6.3)

Mutation pass on patch (60):
- keying the resource colour-space cache with one key for every space
  survived the earlier tests, which used one Indexed resource a page:
  raster::tests::indexed_lookup_cache::two_indexed_resources_are_cached_apart
  kills it;
- the ColorFallback report for a recovered space set with CS had no
  test (only cs was tested): a stroke case in
  a_fill_or_stroke_colour_in_a_short_table_is_padded_and_reported fails
  with that report removed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pq7HyCfwzyRXj4VfQAVVdv

crates/render/src/raster/tests/indexed_lookup_cache.rs

@@ -61,3 +61,15 @@ fn inline_images_naming_one_indexed_resource_read_its_lookup_once() {
     let short = page(20, 7, b"\xFF\x00\x00\x00\xFF\x00");
     assert_eq!(lookup_reads(short), [1, 1], "a short table: read once, then cached");
 }
+
+/// Two Indexed resources whose arrays differ (`/P` names object 5, `/Q` object 6) are two
+/// spaces: each is built, and its table read, once, and neither stands in for the other.
+#[test]
+fn two_indexed_resources_are_cached_apart() {
+    let image = |name: &str| format!("q 20 0 0 20 0 0 cm BI /W 2 /H 1 /BPC 8 /CS /{name} /F /AHx ID 0001> EI Q");
+    let content = [image("P"), image("Q"), image("P"), image("Q")].join("\n");
+    let resources = "<< /ColorSpace << /P [/Indexed /DeviceRGB 1 5 0 R] /Q [/Indexed /DeviceRGB 1 6 0 R] >> >>";
+    let (red_green, blue_white): (&[u8], &[u8]) = (b"\xFF\x00\x00\x00\xFF\x00", b"\x00\x00\xFF\xFF\xFF\xFF");
+    let pdf = image_cache_pdf(&content, resources, &[("<< /Length 6 >>", red_green), ("<< /Length 6 >>", blue_white)]);
+    assert_eq!(lookup_reads(pdf), [2, 2], "each table read once");
+}

crates/render/tests/it/indexed_lookup.rs

@@ -299,10 +299,10 @@ fn an_unreadable_base_keeps_its_fallback() {
     }
 }
 
-/// A fill colour set in such a space (`cs`, `sc`) draws through the same recovered table, and
+/// A fill or stroke colour set in such a space (`cs`, `sc`, `CS`, `SC`) draws through the same recovered table, and
 /// the recovery is reported as `ColourFallback`, as the upstream DeviceGray fallback was.
 #[test]
-fn a_fill_colour_in_a_short_table_is_padded_and_reported() {
+fn a_fill_or_stroke_colour_in_a_short_table_is_padded_and_reported() {
     let fill = |index: u8| format!("/P cs {index} sc 0 0 200 200 re f");
     let short = format!("[/Indexed /DeviceRGB 7 <{}>]", entries(2));
     let page = render(pdf(&short, &fill(1), &[]));
@@ -310,6 +310,10 @@ fn a_fill_colour_in_a_short_table_is_padded_and_reported() {
     assert_eq!(page.warnings, vec![RenderWarning::ColourFallback]);
     let page = render(pdf(&short, &fill(5), &[]));
     assert_eq!(columns(&page)[0], BLACK, "entry 5 is padding");
+    // A stroke colour (`CS`, `SC`) the same way.
+    let page = render(pdf(&short, "/P CS 1 SC 20 w 0 100 m 200 100 l S", &[]));
+    assert_eq!(columns(&page)[0], COLOURS[1], "the stroke is green");
+    assert_eq!(page.warnings, vec![RenderWarning::ColourFallback]);
     let page = render(pdf(&format!("[/Indexed /DeviceRGB 7 <{TABLE}>]"), &fill(1), &[]));
     assert_eq!(columns(&page)[0], COLOURS[1]);
     assert!(page.warnings.is_empty(), "{:?}", page.warnings);