ci: use --ignore-package-exit-codes and harden the version parse, per review

- bash on Windows truncates exit codes to 8 bits, so matching choco's MSI
  reboot codes (1641/3010) by value could never work; choco's
  --ignore-package-exit-codes makes it exit 0 unless it itself detected a
  failure, which also covers 1605/1614.
- The flutter version parse now requires exactly one match and a
  version-shaped result before writing GITHUB_OUTPUT.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: myleshorton

.github/workflows/build-windows.yml

@@ -109,9 +109,15 @@ jobs:
         # on Windows to parse it, and chocolatey.org 504s on that step failed the
         # v9.1.18 and v9.1.19 release builds. The direct version input skips it.
         run: |
-          version=$(sed -n 's/^[[:space:]]*flutter:[[:space:]]*"\{0,1\}\([0-9][^"]*\)"\{0,1\}[[:space:]]*$/\1/p' .github/flutter-version.yaml)
-          if [ -z "$version" ]; then
-            echo "could not parse a flutter version from .github/flutter-version.yaml" >&2
+          matches=$(sed -n 's/^[[:space:]]*flutter:[[:space:]]*"\{0,1\}\([0-9][^"]*\)"\{0,1\}[[:space:]]*$/\1/p' .github/flutter-version.yaml)
+          if [ "$(printf '%s\n' "$matches" | grep -c .)" -ne 1 ]; then
+            echo "expected exactly one flutter version in .github/flutter-version.yaml, got:" >&2
+            printf '%s\n' "$matches" >&2
+            exit 1
+          fi
+          version=$(printf '%s' "$matches" | tr -d '[:space:]')
+          if ! printf '%s' "$version" | grep -qE '^[0-9]+\.[0-9]+\.[0-9]+([-.][0-9A-Za-z.]+)?$'; then
+            echo "parsed flutter version does not look like a version: '$version'" >&2
             exit 1
           fi
           echo "version=$version" >> "$GITHUB_OUTPUT"

scripts/ci/choco-retry.sh

@@ -5,18 +5,20 @@
 # has failed two consecutive Windows release builds (v9.1.18-beta 2026-07-26:
 # mingw + yq; v9.1.19-beta 2026-08-05: yq). A transient feed error should cost
 # a retry, not the build.
+#
+# --ignore-package-exit-codes: MSI success-with-reboot codes (1641/3010) would
+# otherwise surface as nonzero — and 8-bit-truncated by bash on Windows, so
+# unmatchable by value — and read as failures. With the flag, choco exits 0
+# unless it itself detected a failure.
 set -u
 
 for attempt in 1 2 3 4 5; do
-  choco install "$@"
-  code=$?
-  # 1641/3010 are MSI "success, reboot initiated/required" — fine on CI.
-  case $code in
-    0 | 1641 | 3010) exit 0 ;;
-  esac
+  if choco install "$@" --ignore-package-exit-codes; then
+    exit 0
+  fi
   if [ "$attempt" -lt 5 ]; then
     delay=$((attempt * 30))
-    echo "choco install $* exited $code (attempt $attempt/5); retrying in ${delay}s..." >&2
+    echo "choco install $* failed (attempt $attempt/5); retrying in ${delay}s..." >&2
     sleep "$delay"
   fi
 done