fix(micron): preserve multiple spaces under ForceMonospace

ASCII art such as the shadow block logo collapsed consecutive spaces
because appendSplitAtSpaces left plain/space-only segments as bare text.
Parent line divs have white-space: normal, so the browser collapsed the
space runs and broke the layout.

Wrap every split segment:
- plain printable ASCII segments in <span class="Mu-mnt-group">
- non-ASCII or HTML-special segments in <span class="Mu-mws">

This keeps all whitespace in a white-space: pre-wrap span and restores
the rendering that worked in v1.0.7 while keeping the Latin fast path.
Add .Mu-mnt-group to playground CSS and a regression test for multiple
consecutive spaces.

Refs: v1.1.5

Author: Ivan

CHANGELOG.md

@@ -2,6 +2,14 @@
 
 Dates use YYYY-MM-DD.
 
+## [1.1.5] - 2026-09-07
+
+### Fixed
+
+- `ForceMonospace` now preserves multiple consecutive ASCII spaces in Micron markup. Previously, only the first space in a run survived, collapsing ASCII-art whitespace and breaking block-character shading in pages like `shadow`.
+- Plain printable ASCII segments are wrapped in `<span class="Mu-mnt-group">` so the host CSS `white-space: pre-wrap` keeps spacing intact; non-ASCII or HTML-special segments remain in `<span class="Mu-mws">`.
+- Added `.Mu-mnt-group` to the playground CSS so the standalone renderer also keeps whitespace.
+
 ## [1.1.4] - 2026-09-07
 
 ### Added

micron/extra_test.go

@@ -108,3 +108,17 @@ func TestCincinnatusAsciiColor(t *testing.T) {
 		t.Fatalf("expected Mu-mnt cell for block-drawing char: %s", out)
 	}
 }
+
+func TestForceMonospacePreservesMultipleSpaces(t *testing.T) {
+	p := Parser{DarkTheme: true, ForceMonospace: true}
+	out := p.ConvertMicronToHTML("█   █")
+	if stripTags(out) != "█   █" {
+		t.Fatalf("multiple spaces must be preserved in output text, got %q", stripTags(out))
+	}
+	if strings.Count(out, `class="Mu-mnt-group"`) != 2 {
+		t.Fatalf("expected two space-only Mu-mnt-group spans, got: %s", out)
+	}
+	if strings.Count(out, `class="Mu-mnt">█`) != 2 {
+		t.Fatalf("expected two block Mu-mnt cells, got: %s", out)
+	}
+}

micron/split.go

@@ -30,12 +30,14 @@ func splitAfterSpaceSegments(s string) []string {
 }
 
 // appendSplitAtSpaces mirrors micron-parser-js splitAtSpaces / wrapWord.
-// Plain printable ASCII words (no & < >) are emitted unchanged. Words that
-// need escaping or contain non-ASCII are wrapped in Mu-mws, with Mu-mnt cells
-// only around complex grapheme clusters and HTML-special bytes.
+// Every space-delimited segment is wrapped in a whitespace-preserving span so
+// multiple consecutive spaces are not collapsed. Plain printable ASCII words
+// (no & < >) use Mu-mnt-group; words that need escaping or contain non-ASCII
+// use Mu-mws with Mu-mnt cells around complex grapheme clusters and HTML-special
+// bytes.
 func (p *Parser) appendSplitAtSpaces(b *strings.Builder, line string) {
 	if line == "" {
-		b.WriteString(`<span class="Mu-mws"></span>`)
+		b.WriteString(`<span class="Mu-mnt-group"></span>`)
 		return
 	}
 	start := 0
@@ -45,7 +47,16 @@ func (p *Parser) appendSplitAtSpaces(b *strings.Builder, line string) {
 		if rel >= 0 {
 			end = start + rel + 1
 		}
-		p.appendWrapWord(b, line[start:end])
+		word := line[start:end]
+		if wordNeedsMonoWrap(word) {
+			b.WriteString(`<span class="Mu-mws">`)
+			p.appendForceMonospace(b, word)
+			b.WriteString(`</span>`)
+		} else {
+			b.WriteString(`<span class="Mu-mnt-group">`)
+			b.WriteString(word)
+			b.WriteString(`</span>`)
+		}
 		start = end
 	}
 }
@@ -60,19 +71,6 @@ func wordNeedsMonoWrap(word string) bool {
 	return false
 }
 
-func (p *Parser) appendWrapWord(b *strings.Builder, word string) {
-	if word == "" {
-		return
-	}
-	if !wordNeedsMonoWrap(word) {
-		b.WriteString(word)
-		return
-	}
-	b.WriteString(`<span class="Mu-mws">`)
-	p.appendForceMonospace(b, word)
-	b.WriteString(`</span>`)
-}
-
 // isComplexScriptBase reports scripts that must stay as continuous text runs
 // under ForceMonospace. Wrapping each rune in display:inline-block Mu-mnt spans
 // breaks Arabic/Persian joining, Hebrew/RTL order, CJK spacing, and Indic/Thai

web/css/playground.css

@@ -741,6 +741,13 @@ body.preview-only .layout #preview-pane {
   white-space: pre-wrap;
 }
 
+.Mu-mnt-group {
+  display: inline;
+  white-space: pre-wrap;
+  text-decoration: inherit;
+  vertical-align: baseline;
+}
+
 .Mu-partial {
   display: block;
   min-height: 1.2em;