fix(navigation): let CSS size the nav logo and drop the inline width cap

The navbar logo carried an inline `height:36px;width:auto;max-width:{logo_width}px`
while `.navbar-logo > img` already owns `height:36px;padding:0 30px`. Under
`box-sizing:border-box` that max-width capped the border box, so the 60px of
horizontal padding stayed inside it and wide logos were squeezed against a
fixed height, breaking the intrinsic aspect ratio.

- Render the nav logo with no inline sizing; CSS alone sizes it.
- Add a `$lazy` argument to jio_get_adaptive_theme_img() so the navbar can emit
  the real src up front instead of a square lazyload placeholder; defaults to
  'auto' so every other caller keeps the lazy_other behaviour.
- Remove the superseded logo_width plumbing: the setting (PHP + VUE schemas),
  Settings::logo_width(), jio_get_site_logo_width(), the --jio-logo-width token
  and the unused has_logo context key.
- Cover the contract in the header reference test.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

inc/helpers/header/jio-header-render.php

@@ -41,14 +41,12 @@ if (!function_exists('jio_get_header_nav_context')) :
 		$brand_name  = $brand_name !== '' ? $brand_name : $site_name;
 		$logo_url    = function_exists('jio_get_site_logo_url') ? trim((string) jio_get_site_logo_url()) : '';
 		$logo_dark   = function_exists('jio_get_site_logo_dark_url') ? trim((string) jio_get_site_logo_dark_url()) : '';
-		$logo_width  = function_exists('jio_get_site_logo_width') ? jio_get_site_logo_width() : 150;
-		$logo_more   = $logo_width > 0
-			? 'style="height:36px;width:auto;max-width:' . max(36, (int) $logo_width) . 'px"'
-			: 'style="height:36px;width:auto"';
+		// 尺寸由 .navbar-logo > img 统一控制（height:36px / width:auto），
+		// 不叠加内联 max-width，否则 border-box 下的水平内边距会挤压图片。
 		$logo_html   = '';
 		if ($logo_url !== '' || $logo_dark !== '') {
 			$logo_html = function_exists('jio_get_adaptive_theme_img')
-				? jio_get_adaptive_theme_img($logo_url, $logo_dark, $brand_name, $logo_more)
+				? jio_get_adaptive_theme_img($logo_url, $logo_dark, $brand_name, '', false)
 				: '';
 		}
 
@@ -80,7 +78,6 @@ if (!function_exists('jio_get_header_nav_context')) :
 			'scroll_down_hide' => (!isset($settings['nav_scroll_down_hide']) || !empty($settings['nav_scroll_down_hide'])) && $nav_fixed,
 			'brand_name'       => $brand_name,
 			'logo_html'        => $logo_html,
-			'has_logo'         => $logo_html !== '',
 			'theme_positions'  => is_array($theme_positions) ? $theme_positions : [],
 			'can_publish'      => $can_publish,
 			'show_slide'       => $show_slide,