Recognize '2.0' in compatibility inference and CLI badges

Extends the 1.7/1.8 compatibility machinery to treat a grav >= 2.0
dependency as ['2.0']. SelfupgradeCommand's preflight already keys off
the target package's major.minor, so upgrading 1.8 → 2.0 now correctly
flags plugins that only declare 1.7 or 1.8 as blocking.

- GPM/Local/Package::inferCompatibility(): grav >= 2.0 → ['2.0']
- Installer/Install::inferCompatibleVersions(): grav >= 2.0 → ['2.0']
- IndexCommand / InfoCommand / UpdateCommand: magenta '2.0' badge

Ships as part of the final 1.8 beta so the installed base has a clean
upgrade gate when users run `bin/gpm selfupgrade` against a Grav 2.0
release. The actual migration wizard is a 2.0-only deliverable and is
NOT backported here.

system/src/Grav/Common/GPM/Local/Package.php

@@ -91,6 +91,10 @@ class Package extends BasePackage
                 continue;
             }
 
+            if (version_compare($m[1], '2.0', '>=')) {
+                return ['grav' => ['2.0'], 'api' => []];
+            }
+
             if (version_compare($m[1], '1.8', '>=')) {
                 return ['grav' => ['1.8'], 'api' => []];
             }

system/src/Grav/Console/Gpm/IndexCommand.php

@@ -260,6 +260,9 @@ class IndexCommand extends GpmCommand
         if (in_array('1.8', $compat['grav'], true)) {
             $badges[] = '<green>1.8</green>';
         }
+        if (in_array('2.0', $compat['grav'], true)) {
+            $badges[] = '<magenta>2.0</magenta>';
+        }
 
         return implode(' ', $badges);
     }

system/src/Grav/Console/Gpm/InfoCommand.php

@@ -150,6 +150,9 @@ class InfoCommand extends GpmCommand
             if (in_array('1.8', $compat['grav'], true)) {
                 $badges[] = '<green>1.8</green>';
             }
+            if (in_array('2.0', $compat['grav'], true)) {
+                $badges[] = '<magenta>2.0</magenta>';
+            }
             $compatStr = implode(' ', $badges);
         } else {
             $compatStr = '<blue>1.7</blue>';

system/src/Grav/Console/Gpm/UpdateCommand.php

@@ -222,6 +222,9 @@ class UpdateCommand extends GpmCommand
                     if (in_array('1.8', $compat['grav'], true)) {
                         $badges[] = '<green>1.8</green>';
                     }
+                    if (in_array('2.0', $compat['grav'], true)) {
+                        $badges[] = '<magenta>2.0</magenta>';
+                    }
                     $compatStr = ' ' . implode(' ', $badges);
                 }
 

system/src/Grav/Installer/Install.php

@@ -1448,6 +1448,10 @@ ERR;
                 continue;
             }
 
+            if (version_compare($m[1], '2.0', '>=')) {
+                return ['grav' => ['2.0'], 'api' => []];
+            }
+
             if (version_compare($m[1], '1.8', '>=')) {
                 return ['grav' => ['1.8'], 'api' => []];
             }