refactor(HTMLNode): Deprecate duplicate methods and rename applyClass

[usernane]

Description

Several methods are exact delegates with no added logic. These should be consolidated by deprecating the redundant ones and pointing users to the canonical method.

Deprecations

Deprecate	Keep (canonical)	Reason
getAttributeValue($name)	getAttribute($name)	Exact delegate, standard DOM naming
addTextNode($txt, $esc)	text($txt, $esc)	Exact delegate, fluent pattern consistent with br(), hr(), comment()
addCommentNode($txt)	comment($txt)	Exact delegate, same fluent pattern
component($path, $vals)	include($path, $vals)	Exact delegate, already marked deprecated in source
getName()	getAttribute('name')	Trivial shortcut, confusing next to getNodeName()
setName($val)	setAttribute('name', $val)	Trivial shortcut, confusing next to setNodeName()
applyClass($cName, $override)	applyClassToChildren($cName, $override, $depth)	Misleading name (see below)

Removals (dead code)

Remove	Reason
private $null property	Unused, assigned null in constructor, never read
isUseOriginalText()	Already @deprecated, no internal references
$useOriginalTxt property	Only supports the deprecated method above

Keep Both (no deprecation)

Method	Reason
count()	Required by Countable interface for count($node)
childrenCount()	Explicit named method, different use case

New Method: applyClassToChildren()

applyClass() applies a class to all children, not to the node itself. The name is misleading. Replace with:

public function applyClassToChildren(string $cName, bool $override = true, int $depth = 1): HTMLNode {
    if ($depth < 1) {
        return $this;
    }
    foreach ($this as $child) {
        $child->setClassName($cName, $override);
        if ($depth > 1 && !$child->isVoidNode()) {
            $child->applyClassToChildren($cName, $override, $depth - 1);
        }
    }
    return $this;
}

• $depth = 1 — direct children only (default, matches current behavior)
• $depth = 2 — children + grandchildren
• $depth = PHP_INT_MAX — all descendants

Acceptance Criteria

• Deprecated methods have @deprecated tag pointing to the canonical method
• Deprecated methods still function (no removal yet)
• applyClassToChildren() added with $depth parameter
• Dead code ($null, isUseOriginalText(), $useOriginalTxt) removed
• All 308 tests pass