[css-counter-styles] Remove more mentions of insufficient 'symbols' length making things invalid, and put an explainer about the length req into 'system' as well. Fixes w3c#5717.

Author: tabatkins

css-counter-styles-3/Overview.bs

@@ -235,6 +235,13 @@ Counter algorithms: the 'system' descriptor</h3>
 	build their representation accordingly.
 	The systems are defined in the following subsections.
 
+	Each 'system' value is associated with either the 'symbols' or 'additive-symbols' descriptors,
+	and has a minimum length that the appropriate descriptor must have;
+	each entry below defines what this is.
+	If a ''@counter-style'' rule fails to meet this requirement,
+	it does not define a [=counter style=].
+	(The rule is still syntactically valid, but has no effect.)
+
 <!--
  ██████  ██    ██  ██████  ██       ████  ██████
 ██    ██  ██  ██  ██    ██ ██        ██  ██    ██
@@ -257,8 +264,7 @@ Cycling Symbols: the ''cyclic'' system</h4>
 	the second <a>counter symbol</a> (if it exists) is used as the representation of the value 2, etc.
 
 	If the system is ''cyclic'',
-	the 'symbols' descriptor must contain at least one <a>counter symbol</a>,
-	or else the ''@counter-style'' rule is invalid.
+	the 'symbols' descriptor must contain at least one <a>counter symbol</a>.
 	This system is defined over all counter values.
 
 	<div class=example>
@@ -307,8 +313,7 @@ Exhaustible Symbols: the ''system/fixed'' system</h4>
 	such as circled digits.
 
 	If the system is ''system/fixed'',
-	the 'symbols' descriptor must contain at least one <a>counter symbol</a>,
-	or else the ''@counter-style'' rule is invalid.
+	the 'symbols' descriptor must contain at least one <a>counter symbol</a>.
 	This system is defined over counter values in a finite range,
 	starting with the <a>first symbol value</a> and having a length equal to the length of the list of <a>counter symbols</a>.
 
@@ -368,8 +373,7 @@ Repeating Symbols: the ''symbolic'' system</h4>
 	and is also sometimes used for alphabetic-style lists for a slightly different presentation than what the ''system/alphabetic'' system presents.
 
 	If the system is ''symbolic'',
-	the 'symbols' descriptor must contain at least one <a>counter symbol</a>,
-	or else the ''@counter-style'' rule is invalid.
+	the 'symbols' descriptor must contain at least one <a>counter symbol</a>.
 	This system is defined only over strictly positive counter values.
 
 	<div class=example>
@@ -457,8 +461,7 @@ Bijective Numerals: the ''alphabetic'' system</h4>
 	and so on.
 
 	If the system is ''system/alphabetic'',
-	the 'symbols' descriptor must contain at least two <a>counter symbols</a>,
-	or else the ''@counter-style'' rule is invalid.
+	the 'symbols' descriptor must contain at least two <a>counter symbols</a>.
 	This system is defined only over strictly positive counter values.
 
 	<div class=example>
@@ -530,8 +533,7 @@ Positional Numerals: the ''numeric'' system</h4>
 	and so on.
 
 	If the system is ''system/numeric'',
-	the 'symbols' descriptor must contain at least two <a>counter symbols</a>,
-	or else the ''@counter-style'' rule is invalid.
+	the 'symbols' descriptor must contain at least two <a>counter symbols</a>.
 	This system is defined over all counter values.
 
 	<div class=example>
@@ -602,8 +604,7 @@ Accumulating Numerals: the ''additive'' system</h4>
 	and other numbering systems around the world.
 
 	If the system is ''additive'',
-	the 'additive-symbols' descriptor must contain at least one <a>additive tuple</a>,
-	or else the ''@counter-style'' rule is invalid.
+	the 'additive-symbols' descriptor must contain at least one <a>additive tuple</a>.
 	This system is nominally defined over all counter values
 	(see algorithm, below, for exact details).