ci: update version.json from a single place (#375)

- Fixes a broken pipeline: the `single_update` branch had a
half-migrated step that pre-wrote `flutter_version.json` before the JS
comparator ran, causing every scheduled run to emit `result=false` and
skip all downstream jobs — meaning no update PRs were ever opened
- Replaces `script/updateFlutterVersion.js` with a single shell+jq step
that fetches `releases_linux.json`, reads the pinned version, compares,
and only writes when the upstream stable version actually changed
- Sources `android.buildTools.version` from Flutter's own
`engine/src/flutter/tools/android_sdk/packages.txt` at the new tag
(instead of being orphaned with no write path into `version.json`)
- Fixes `config/schema.cue` undefined reference (`#PatchVersion` →
`#SemverPatch`) that caused `cue vet` to fail
- Fixes `config/android.cue` length guard typo (`fileContentTests` →
`commandTests`)
- Fixes the PR creation step writing `commit_message` to `$GITHUB_ENV`
instead of `$GITHUB_OUTPUT`, which resulted in PRs with empty titles and
commit messages

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

config/android.cue

@@ -36,25 +36,27 @@ output: {
 	
 	commandTests: list.Concat([
 		list.Take(input.commandTests, 1),
-		[
-			{
-				name: input.commandTests[1].name
-				command: input.commandTests[1].command
-				args: input.commandTests[1].args
-				expectedOutput: [android_sdk_build_tools_version]
-			},
-			{
-				name: input.commandTests[2].name
-				command: input.commandTests[2].command
-				args: input.commandTests[2].args
-				expectedOutput: [android_ndk_version]
-			}
-		],
+		if len(input.commandTests) >= 3 {
+			[
+				{
+					name: input.commandTests[1].name
+					command: input.commandTests[1].command
+					args: input.commandTests[1].args
+					expectedOutput: [android_sdk_build_tools_version]
+				},
+				{
+					name: input.commandTests[2].name
+					command: input.commandTests[2].command
+					args: input.commandTests[2].args
+					expectedOutput: [android_ndk_version]
+				}
+			]
+		},
 		list.Drop(input.commandTests, 3),
 	])
 	
 	fileContentTests: list.Concat([
-		if len(input.fileContentTests) > 0 {
+		if len(input.fileContentTests) >= 1 {
 			[{
 				name: "Android SDK Command-line Tools is version \(android_cmdline_tools_version)"
 				path: input.fileContentTests[0].path

config/flutter_version.cue

@@ -1,12 +0,0 @@
-import "strings"
-import "list"
-
-#Version3: {
-	version!: =~ "^\\d+.\\d+.\\d+$"
-}
-
-flutter: {
-	channel!: "stable" | "beta"
-	commit!:  strings.MaxRunes(40)
-	#Version3
-}

config/schema.cue

@@ -5,35 +5,35 @@ import "list"
 	version!: int
 }
 
-#MinorVersion: {
+#SemverMinor: {
 	version!: =~ "^\\d+.\\d+$"
 }
 
-#PatchVersion: {
+#SemverPatch: {
 	version!: =~ "^\\d+.\\d+.\\d+$"
 }
 
 #FlutterVersion: {
 	flutter: {
-		channel!: "stable" | "beta"
+		channel!: "stable"
 		commit!:  strings.MaxRunes(40)
-		#PatchVersion
+		#SemverPatch
 	}
 }
 
-#MinorOrPatchVersion: #MinorVersion | #PatchVersion
+#SemverVersion: #SemverMinor | #SemverPatch
 
 #Version: {
 	#FlutterVersion
 
 	android: {
 		platforms!: [...#PlatformVersion] & list.MinItems(1) & list.UniqueItems
-		gradle!: #MinorOrPatchVersion
-		buildTools!: #PatchVersion
-		cmdlineTools!: #MinorVersion
-		ndk!: #PatchVersion
-		cmake!: #PatchVersion
+		gradle!: #SemverVersion
+		buildTools!: #SemverPatch
+		cmdlineTools!: #SemverMinor
+		ndk!: #SemverPatch
+		cmake!: #SemverPatch
 	}
 
-	fastlane!: #PatchVersion
+	fastlane!: #SemverPatch
 }