Trim comments that restate or argue

The operand order was written out in three places; it now lives at calcVars,
which fixes it, and the other two point there. Dropped the note explaining
why ')' is not reserved, which said what the set is not rather than what it
is, and shortened reservedList's doc to less than its body. The note on held
now states where it reaches instead of arguing against a design this repo no
longer contains.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

node.go

@@ -257,11 +257,9 @@ func weightOf(raw any) (float64, error) {
 // separates the segments of a path, '|' the arms of a token, '(' opens a function
 // call and '}' ends the token. A name carrying one is reachable by no format, so it
 // is rejected where it is authored rather than at the token that cannot reach it.
-// ')' is absent deliberately — it is spellable on its own, so it stays legal.
 const reservedInName = ".|(}"
 
-// reservedList is reservedInName spelled out for an error message, so the two
+// reservedList spells reservedInName for an error message, so the two cannot drift.
-// cannot drift apart.
 var reservedList = strings.Join(strings.Split(reservedInName, ""), " ")
 
 // checkName rejects a name the dot path and {token} grammars cannot spell. Both a

render.go

@@ -138,8 +138,8 @@ func expand(s *session, t *template) string {
 	var b strings.Builder
 	b.Grow(t.grow)
 	// One draw per held name, for this expansion only: a nested template and each
-	// repeat iteration get their own, since each is its own expansion. held stays a
+	// repeat iteration get their own, since each is its own expansion. held reaches
-	// local: nothing hands it to a builtin, so it and its maps never leave the stack.
+	// no further than readField, which keeps it and its maps on the stack.
 	var held *draws
 	if len(t.held) > 0 {
 		held = &draws{
@@ -157,8 +157,7 @@ func expand(s *session, t *template) string {
 		case 'f':
 			b.WriteString(readField(s, t, held, o.arms[s.IntN(len(o.arms))]))
 		case 'b':
-			// A calc's operands are read here, in the order its expression first
+			// Read in the order calcVars fixed, which is what op.operands holds.
-			// names them, so the value it computes is the value the format showed.
 			var operands []string
 			if len(o.operands) > 0 {
 				operands = make([]string, len(o.operands))

template.go

@@ -317,9 +317,8 @@ type op struct {
 	r    rune   // kind 'c'
 	arms []arm  // kind 'f': the '|' alternatives, split into key and path once
 	call callFn
-	// operands names the sibling fields a {calc()} reads, in the order its
+	// operands names the sibling fields a {calc()} reads, in the order calcVars
-	// expression first names them. expand reads them before the call, so the
+	// fixed; expand reads them before the call. nil for every other builtin.
-	// evaluator never touches the node tree. nil for every other builtin.
 	operands []string
 }