Add compatibility preflight to upgrade flow + compatibility badges

Gpm::upgradeGrav() now calls generatePreflightReport() from the new
package's Install.php before proceeding. If incompatible plugins are
detected, a detailed error message is shown listing which plugins need
to be disabled.

Adds colored compatibility badges (1.7 blue, 1.8 green) to:
- Plugin list, theme list, and plugin detail views
- SCSS badge styles (.gpm-compat-17, .gpm-compat-18, .gpm-compat-api)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

classes/plugin/Gpm.php

@@ -423,6 +423,25 @@ class Gpm
             $script = $folder . '/system/install.php';
             /** Install $installer */
             if ((file_exists($script) && $install = include $script) && is_callable($install)) {
+                // Run preflight from the NEW package's installer if available
+                if (is_object($install) && method_exists($install, 'generatePreflightReport')) {
+                    $report = $install->generatePreflightReport();
+                    $blocking = $report['blocking'] ?? [];
+                    $incompatible = $report['incompatible_packages'] ?? [];
+
+                    if (!empty($blocking) || !empty($incompatible['blocking'])) {
+                        $errors = [];
+                        foreach ($blocking as $reason) {
+                            $errors[] = $reason;
+                        }
+                        foreach ($incompatible['blocking'] ?? [] as $slug => $info) {
+                            $errors[] = sprintf('<strong>%s</strong> (%s v%s) — not compatible with Grav %s. Disable it to proceed.',
+                                $slug, $info['type'] ?? 'plugin', $info['version'] ?? '?', $incompatible['target'] ?? '?');
+                        }
+                        Installer::setError(implode('<br>', $errors));
+                        return;
+                    }
+                }
                 $install($zip);
             } else {
                 Installer::install(

themes/grav/scss/template/_gpm.scss

@@ -84,6 +84,29 @@
         line-height: 1.3;
     }
 
+    .gpm-compat {
+        @extend .badge;
+        border-radius: 3px;
+        padding: 0 4px;
+        font-size: 0.75rem;
+        margin-left: 2px;
+    }
+
+    .gpm-compat-17 {
+        background: #3b82f6;
+        color: white;
+    }
+
+    .gpm-compat-18 {
+        background: #22c55e;
+        color: white;
+    }
+
+    .gpm-compat-api {
+        background: #06b6d4;
+        color: white;
+    }
+
     .gpm-actions {
 
         .enabled, .disabled {

themes/grav/templates/partials/plugin-data.html.twig

@@ -49,6 +49,18 @@
         </tr>
     {% endif %}
 
+    <tr>
+        <td>Compatibility:</td>
+        <td class="double">
+            {% set compat = plugin.compatibility.grav ?? ['1.7'] %}
+            {% if '1.7' in compat %}<span class="gpm-compat gpm-compat-17">1.7</span>{% endif %}
+            {% if '1.8' in compat %}<span class="gpm-compat gpm-compat-18">1.8</span>{% endif %}
+            {% if plugin.compatibility.api is defined %}
+                {% for v in plugin.compatibility.api %}<span class="gpm-compat gpm-compat-api">api:{{ v }}</span>{% endfor %}
+            {% endif %}
+        </td>
+    </tr>
+
     {% if plugin.description %}
         <tr>
             <td>{{ "PLUGIN_ADMIN.DESCRIPTION"|t }}:</td>

themes/grav/templates/partials/plugins-list.html.twig

@@ -41,6 +41,9 @@
                 {% endif %}
                 <span class="gpm-version">v{{ plugin.version }}</span>
                 {% if isTestingRelease %}<span class="gpm-testing">test release</span>{% endif %}
+                {% set compat = plugin.compatibility.grav ?? ['1.7'] %}
+                {% if '1.7' in compat %}<span class="gpm-compat gpm-compat-17">1.7</span>{% endif %}
+                {% if '1.8' in compat %}<span class="gpm-compat gpm-compat-18">1.8</span>{% endif %}
             </td>
             <td class="gpm-actions">
                 {% if (not installing and (plugin.form.fields.enabled.type != 'hidden' and plugin.form.fields.tabs.fields.options.fields.enabled.type != 'hidden')) %}

themes/grav/templates/partials/themes-list.html.twig

@@ -43,6 +43,9 @@
                 {% endif %}
                 <span class="gpm-version">v{{ theme.version }}</span>
                 {% if isTestingRelease %}<span class="gpm-testing">test release</span>{% endif %}
+                {% set compat = theme.compatibility.grav ?? ['1.7'] %}
+                {% if '1.7' in compat %}<span class="gpm-compat gpm-compat-17">1.7</span>{% endif %}
+                {% if '1.8' in compat %}<span class="gpm-compat gpm-compat-18">1.8</span>{% endif %}
             </div>
             <div class="gpm-screenshot">
                 {% set thumb = installing ? '//getgrav.org/images/' ~ theme.screenshot : theme.thumbnail %}