feat(appstore): script the provisioning, listing and TestFlight setup

The listing copy lives in text files rather than in a web form, so changing a description is a diff
someone can read and the store listing is reviewable next to the code it describes. Field lengths
are checked before sending, because Apple rejects an over-length field with an error that never
names the limit.

apple-provision.rb drives the Developer Portal through spaceship and is find-or-create throughout.
That matters most for the Developer ID certificate: an account may hold only a handful, they cannot
be un-revoked, and every copy of the app already signed by one stops verifying if it goes away.

Both scripts pin the App Store Connect team. This Apple ID can see more than one, and the other
belongs to somebody else entirely, so letting spaceship choose is how a listing ends up on the
wrong account.

The reviewer phone number and email are deliberately not in here. Apple requires a real number and
this repo is public.

Claude-Session: https://claude.ai/code/session_018HwEWvoE1NkkUjJCMLSnup

scripts/apple-secrets.sh

@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+# Push everything apple-provision.rb produced into this repo's GitHub Actions secrets.
+#
+# Values are piped from the files straight into `gh`, never echoed, so running this in a shared
+# terminal or through an agent does not leak a signing key into the scrollback.
+set -euo pipefail
+
+DIR="${MARGIN_SIGNING_DIR:-$HOME/.margin-signing}"
+BUNDLE_ID="${BUNDLE_ID:-studio.margin.app}"
+REPO="${REPO:-priyanshujain/margin}"
+ENV_FILE="$DIR/$BUNDLE_ID.env"
+
+[ -f "$ENV_FILE" ] || { echo "apple-secrets: $ENV_FILE is missing; run apple-provision.rb first." >&2; exit 1; }
+# shellcheck source=/dev/null
+set -a; . "$ENV_FILE"; set +a
+
+set_plain() {
+  printf '%s' "$2" | gh secret set "$1" --repo "$REPO" --body -
+  echo "  set $1"
+}
+
+set_b64() {
+  [ -f "$2" ] || { echo "  skipped $1 ($2 is missing)"; return; }
+  base64 -i "$2" | tr -d '\n' | gh secret set "$1" --repo "$REPO" --body -
+  echo "  set $1"
+}
+
+set_file() {
+  [ -f "$2" ] || { echo "  skipped $1 ($2 is missing)"; return; }
+  gh secret set "$1" --repo "$REPO" < "$2"
+  echo "  set $1"
+}
+
+echo "Signing identities and team:"
+set_plain APPLE_TEAM_ID "$APPLE_TEAM_ID"
+set_plain APPLE_SIGNING_IDENTITY "$APPLE_SIGNING_IDENTITY"
+set_plain MAS_APP_IDENTITY "$MAS_APP_IDENTITY"
+set_plain MAS_INSTALLER_IDENTITY "$MAS_INSTALLER_IDENTITY"
+
+echo "Certificates:"
+set_b64  APPLE_CERTIFICATE "$DIR/developer-id.p12"
+set_file APPLE_CERTIFICATE_PASSWORD "$DIR/developer-id.p12.pass"
+set_b64  MAS_APP_CERTIFICATE "$DIR/apple-distribution.p12"
+set_file MAS_APP_CERTIFICATE_PASSWORD "$DIR/apple-distribution.p12.pass"
+set_b64  MAS_INSTALLER_CERTIFICATE "$DIR/mac-installer.p12"
+set_file MAS_INSTALLER_CERTIFICATE_PASSWORD "$DIR/mac-installer.p12.pass"
+set_b64  MAS_PROVISION_PROFILE "$DIR/$BUNDLE_ID.provisionprofile"
+
+echo "App Store Connect API key:"
+if [ -f "$DIR/AuthKey.p8" ] && [ -f "$DIR/AuthKey.env" ]; then
+  # shellcheck source=/dev/null
+  set -a; . "$DIR/AuthKey.env"; set +a
+  # An empty value here would be accepted by `gh` and then fail notarization as an auth error that
+  # says nothing about a missing issuer, so refuse it at the point the mistake is still visible.
+  if [ -z "${APPLE_API_KEY_ID:-}" ] || [ -z "${APPLE_API_ISSUER:-}" ]; then
+    echo "  refused: AuthKey.env is missing APPLE_API_KEY_ID or APPLE_API_ISSUER." >&2
+    exit 1
+  fi
+  set_plain APPLE_API_KEY_ID "$APPLE_API_KEY_ID"
+  set_plain APPLE_API_ISSUER "$APPLE_API_ISSUER"
+  set_b64   APPLE_API_KEY_P8 "$DIR/AuthKey.p8"
+else
+  echo "  skipped: put the .p8 at $DIR/AuthKey.p8 and write $DIR/AuthKey.env with"
+  echo "           APPLE_API_KEY_ID= and APPLE_API_ISSUER=, then rerun."
+fi
+
+echo
+echo "Not handled here: HOMEBREW_TAP_DEPLOY_KEY, an SSH deploy key on the tap rather than"
+echo "anything Apple issued."