fix: add { to glob-char guards and use single-pass template replacer

Three correctness fixes found during round-3 code review:

1. validatePathEntry (allowGlob=false) was missing { from the rejected
   glob metacharacter set. The comment already documented { as forbidden
   for outputs; the code now enforces it consistently with *, ?, and [.

2. isGlobPattern in locate.go used "*?[" — missing { for brace expansion
   ({a,b}) which doublestar supports. Misclassifying a brace-glob input
   as a literal path caused LSP go-to-definition to navigate to a
   nonexistent file. Now matches hasGlobMeta in linkgraph/directives.go.

3. generateBody used two sequential strings.ReplaceAll calls. If an
   output path contained {alt}, the first pass would introduce {alt}
   into the body and the second pass would expand it again. Replaced
   with strings.NewReplacer (single-pass, immune to this).

https://claude.ai/code/session_0166NMrRbK1uDGk847FENqZ9

Author: claude

internal/index/locate.go

@@ -485,7 +485,7 @@ var piArgRE = regexp.MustCompile(`^\s*([A-Za-z_][A-Za-z0-9_-]*)\s*:\s*(.*?)\s*$`
 var piListItemRE = regexp.MustCompile(`^\s*-\s+(.*?)\s*$`)
 
 // isGlobPattern reports whether p contains doublestar glob metacharacters.
-func isGlobPattern(p string) bool { return strings.ContainsAny(p, "*?[") }
+func isGlobPattern(p string) bool { return strings.ContainsAny(p, "*?[{") }
 
 // headingOnLine returns the heading whose first source line equals
 // line, or nil.

internal/index/locate_coverage_test.go

@@ -270,3 +270,14 @@ func TestLocateBuildDirectiveInputsLiteral(t *testing.T) {
 	assert.Equal(t, "inputs", res.DirectiveArg)
 	assert.Equal(t, "src.svg", res.DirectiveTargetFile)
 }
+
+// TestLocateBuildDirectiveInputsBraceGlob: brace-expansion inputs must not set DirectiveTargetFile.
+func TestLocateBuildDirectiveInputsBraceGlob(t *testing.T) {
+	t.Parallel()
+	src := "# T\n\n<?build\nrecipe: render\noutputs:\n  - \"out.png\"\ninputs:\n  - \"{a,b}.md\"\n?>\n<?/build?>\n"
+	res := Locator{Path: "a.md"}.Locate([]byte(src), 8, 5)
+	assert.Equal(t, TokenDirectiveArg, res.Tag)
+	assert.Equal(t, "build", res.DirectiveName)
+	assert.Equal(t, "inputs", res.DirectiveArg)
+	assert.Empty(t, res.DirectiveTargetFile, "brace-expansion input must not set DirectiveTargetFile")
+}

internal/rules/build/rule.go

@@ -296,8 +296,7 @@ func (r *Rule) generateBody(
 	rendered := make([]string, 0, len(outputs))
 	for _, output := range outputs {
 		alt := fmt.Sprintf("%s output: %s", recipeName, output)
-		body := strings.ReplaceAll(tmpl, "{output}", output)
-		body = strings.ReplaceAll(body, "{alt}", alt)
+		body := strings.NewReplacer("{output}", output, "{alt}", alt).Replace(tmpl)
 		rendered = append(rendered, body)
 	}
 	body := strings.Join(rendered, "\n")
@@ -370,7 +369,7 @@ func validatePathEntry(p string, allowGlob bool) string {
 	if strings.HasPrefix(p, "/") || strings.HasPrefix(p, "~") {
 		return "must be a relative path"
 	}
-	if !allowGlob && strings.ContainsAny(p, "*?[") {
+	if !allowGlob && strings.ContainsAny(p, "*?[{") {
 		return "must not contain glob characters"
 	}
 	cleaned := path.Clean(p)

internal/rules/build/rule_test.go

@@ -753,7 +753,7 @@ func TestValidatePathEntry_UnderMdsmithDir(t *testing.T) {
 }
 
 func TestValidatePathEntry_OutputsRejectGlobChars(t *testing.T) {
-	for _, p := range []string{"out*.png", "out?.png", "out[1].png"} {
+	for _, p := range []string{"out*.png", "out?.png", "out[1].png", "out{a,b}.png"} {
 		assert.NotEmpty(t, validatePathEntry(p, false), "path %q should be rejected for outputs", p)
 	}
 }