feat(websem,textlayout): render <text> — the text rung

The Web family gains a real shaped-text producer, and <text> leaves the
refusal corpus for six Chromium-baked cells.

The document says, the oracle resolves:

- websem's <text> arm owns source semantics only — character data with
  XML whitespace collapsing (measured: a tab, a newline, and a run of
  spaces each collapse to one advance), x/y, text-anchor, and the
  cascaded family and size. It shapes nothing.
- textlayout resolves the run once against a declared font environment
  and returns the immutable artifact; glyph outlines lower to rframe's
  existing path facts, so no font identity crosses the contract and the
  frame stays honestly glyphless.
- the admitted numeric domain is enforced, not assumed: integer position,
  font-size a multiple of 5, integer anchor-resolved start. Chromium
  snaps everything else by a rasterizer-internal rule; this refuses by
  name rather than codifying it.

Hermetic by default: a run whose family the host never declared refuses
by name — no tofu, no ambient face, no machine-local pixel. A generic
family (including the initial value) names no declared font and says so.

fixtures/web-first/text/ is the suite, on the animation/ precedent and
under the corpus-growth law: the fixture is the document, the font is
the environment, and the baker declares the pinned identity to Chromium
exactly as the host declares it to the engine — verified against its
digest before any capture. All six cells are byte-exact with no
tolerance admissible.

svg-text graduates; what remains refused holds its own rows
(svg-text-undeclared-font, svg-text-tspan). Two legacy expectations move
with the behavior: basic-shapes.svg's stylesheet declares text-anchor
and its labels ask for a generic family — both were silent drops before
this rung and are named holes after it.

Author: softmarshmallow

Cargo.lock

@@ -121,7 +121,10 @@ fn standalone_svg_presentation_hints_enter_below_author_rules() {
     // Measured in Chromium: the attribute alone selects the face, an author
     // rule beats it, `font-family=""` drops to the default family, and the
     // property inherits.
-    assert_eq!(property(root, "family-hint", LonghandId::FontFamily), "Ahem");
+    assert_eq!(
+        property(root, "family-hint", LonghandId::FontFamily),
+        "Ahem"
+    );
     assert_eq!(
         property(root, "family-rule-beats-hint", LonghandId::FontFamily),
         "monospace"

crates/csscascade/tests/svg_presentation_hints.rs

@@ -435,13 +435,15 @@ mod tests {
         let root = Path::new(env!("CARGO_MANIFEST_DIR")).join("../..");
         for (relative, kind, size, named) in [
             (
-                // The strokes rung consumed this fixture's stroked shapes and
-                // its two `<line>`s, so strict now reaches the labels: the
-                // first refusal is `<text>`, the next rung on the ladder.
+                // The text rung admitted `<text>` itself, so strict now
+                // reaches this fixture's *stylesheet* first: `.label`
+                // declares `text-anchor`, which Chromium consumes from the
+                // cascade and the pinned servo build cannot represent. It
+                // was a silent drop before that row existed.
                 "fixtures/test-svg/L0/basic-shapes.svg",
                 SourceKind::Svg,
                 (500, 500),
-                "unsupported element <text>",
+                "a stylesheet declares text-anchor",
             ),
             (
                 // The probe's `.mark` class CSS-sizes the inline <svg>:
@@ -485,6 +487,12 @@ mod tests {
         // because Chromium paints nothing for them either. After the points
         // rung the polygons and the polyline render too, so what remains is
         // the labels and one rounded rect (`rx` is not consumed).
+        //
+        // After the text rung the labels are still declared, for reasons
+        // that moved one layer up: the sheet's `text-anchor` cannot be
+        // represented (declared once at `svg/style[1]`), and each label asks
+        // for the generic `monospace`, which names no font in a declared
+        // environment. Both are named holes where a silent drop used to be.
         let source = std::fs::read_to_string(root.join("fixtures/test-svg/L0/basic-shapes.svg"))
             .expect("read basic-shapes");
         let (png, degradations) = render_source_to_png(
@@ -506,6 +514,7 @@ mod tests {
         assert_eq!(
             skipped,
             vec![
+                "svg/style[1]",
                 "svg/g[1]/text[1]",
                 "svg/g[2]/rect[1]",
                 "svg/g[2]/text[1]",
@@ -521,8 +530,15 @@ mod tests {
         assert!(
             degradations
                 .iter()
-                .any(|d| d.reason() == "unsupported element <text>"),
-            "reasons name the construct"
+                .any(|d| d.reason().contains("a stylesheet declares text-anchor")),
+            "the sheet's unrepresentable declaration is named once"
+        );
+        assert!(
+            degradations
+                .iter()
+                .any(|d| d.reason().contains("generic font family")),
+            "the labels' `font-family: monospace` names no declared font, and the run says so \
+             instead of falling back to an ambient face"
         );
         assert!(
             !degradations.iter().any(|d| d.path() == "svg/g[1]"),

crates/n0_cli/src/main.rs

@@ -16,6 +16,10 @@ cg = { path = "../cg" }
 # The source-neutral resolved render contract this crate produces.
 # Contract-only and backend-free; the n0 engine owns the one downstream.
 rframe = { path = "../rframe" }
+# The Web family's text resolution oracle (the text rung): websem states what
+# the document says, textlayout states what the glyphs are. No font byte and
+# no ambient face enters through this edge — the environment is the host's.
+textlayout = { path = "../textlayout" }
 # Neutral geometry.
 math2 = { path = "../math2" }
 # The one namespace-aware document + the one (Stylo) browser-grade cascade.

crates/websem/Cargo.toml

@@ -27,6 +27,7 @@ pub mod svg;
 mod svg_animation;
 mod svg_paint_server;
 mod svg_path;
+mod svg_text;
 mod svg_transform;
 
 pub use svg::{