Sign builds and releases with a stable code identity

swiftc linker-signs only the inner binary, leaving the bundle unsigned
and its codesign identifier as "launcher" rather than the bundle id. More
importantly it leaves the app ad-hoc signed, and macOS pins an ad-hoc
app's Accessibility grant to its exact cdhash instead of to a designated
requirement. Every build mints a new cdhash, so each rebuild-and-replace
silently revoked the permission while the app stayed listed and ticked
under Privacy & Security — and every release did the same to everyone who
updated. That was the root cause of the window tags never appearing.

- build.sh signs the bundle with its real identifier, honours
  SHANNONCOAT_SIGN_IDENTITY, and fails outright rather than falling back
  to ad-hoc when an identity was asked for explicitly.
- The identity is read from a gitignored .env, so it doesn't have to be
  retyped every build. Parsed rather than sourced, so a stray command in
  the file can't execute as a side effect of building, and so an existing
  environment variable still wins. .env.example carries the full one-time
  setup.
- release.yml imports the certificate into a throwaway keychain, builds,
  verifies, and deletes the keychain on if: always(). It stays inert
  until the three secrets exist, and fails the release rather than
  shipping ad-hoc.
- Guards the empty-password case explicitly: macOS cannot import an
  OpenSSL-produced PKCS#12 with an empty password, and reports it as "MAC
  verification failed (wrong password?)", which sends you hunting for a
  wrong password rather than a missing one. Nothing local catches this,
  since the login keychain imports the PEM pair and needs no password.
- Ignores *.p12 and *.pem as a backstop; the certificate belongs outside
  the working tree entirely.

Verified end-to-end: two from-scratch builds produce byte-identical
designated requirements where ad-hoc differs every time, and six
rebuild-reinstall cycles under a real certificate kept the Accessibility
grant with no System Settings interaction.

This buys permission persistence, not Gatekeeper approval — a
self-signed certificate isn't notarized, so downloads still need
System Settings -> Privacy & Security -> Open Anyway.

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

build.sh

@@ -13,6 +13,29 @@ set -euo pipefail
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 SOURCES_DIR="$SCRIPT_DIR/Sources"
+
+# Local, gitignored build configuration — currently just the code-signing
+# identity, which otherwise has to be remembered and retyped on every
+# build. See .env.example.
+#
+# Parsed rather than sourced, for two reasons: a stray command in the file
+# shouldn't execute as a side effect of building, and this lets an existing
+# environment variable win, so `SHANNONCOAT_SIGN_IDENTITY= ./build.sh`
+# still forces a one-off ad-hoc build without editing the file.
+ENV_FILE="$SCRIPT_DIR/.env"
+if [[ -f "$ENV_FILE" ]]; then
+  while IFS='=' read -r key value || [[ -n "$key" ]]; do
+    key="${key#"${key%%[![:space:]]*}"}"   # strip leading whitespace
+    key="${key#export }"
+    [[ "$key" =~ ^[A-Za-z_][A-Za-z0-9_]*$ ]] || continue   # skips blanks and # comments
+    value="${value%"${value##*[![:space:]]}"}"             # strip trailing whitespace
+    value="${value%\"}"; value="${value#\"}"
+    value="${value%\'}"; value="${value#\'}"
+    [[ -n "${!key+set}" ]] && continue                     # already in the environment; leave it
+    printf -v "$key" '%s' "$value"
+    export "${key?}"
+  done <"$ENV_FILE"
+fi
 VERSION_FILE="$SCRIPT_DIR/VERSION"
 ICON_SRC="$SCRIPT_DIR/icon/AppIcon.icns"
 OUT_DIR="${1:-$SCRIPT_DIR/.build}"
@@ -76,6 +99,41 @@ printf '%s' "$GIT_SHA" >"$APP/Contents/Resources/COMMIT"
 
 swiftc -O "$SOURCES_DIR"/*.swift -o "$APP/Contents/MacOS/launcher"
 
+# Sign the bundle, not just the binary swiftc linker-signed for us — and
+# with the bundle's real identifier rather than the "launcher" executable
+# name codesign would otherwise infer.
+#
+# This matters well beyond tidiness, because the window tags need
+# Accessibility. macOS ties that grant to a *properly signed* app's
+# designated requirement, which survives a rebuild, but falls back to
+# pinning an ad-hoc-signed app to its exact cdhash — and every build
+# produces a new one. So with the ad-hoc default below, each build +
+# reinstall silently invalidates the permission, while the app stays
+# listed and stays ticked under Privacy & Security → Accessibility. It
+# looks granted and isn't, and no amount of toggling that row fixes it:
+# the stale entry has to be removed with "−" and the new build added back.
+#
+# To stop paying that tax on every build, make a self-signed code-signing
+# certificate once (Keychain Access → Certificate Assistant → Create a
+# Certificate…, type "Code Signing", self-signed) and point this at it:
+#
+#   SHANNONCOAT_SIGN_IDENTITY="My Local Signing Cert" ./build.sh
+#
+# then re-grant Accessibility one final time. The identity is stable from
+# then on, so later builds keep the permission.
+if [[ -n "${SHANNONCOAT_SIGN_IDENTITY:-}" ]]; then
+  # An identity was asked for explicitly, so falling back to ad-hoc would
+  # quietly reintroduce the very problem it was set to avoid — and a
+  # release that ships ad-hoc revokes the Accessibility permission of
+  # everyone who updates. Fail the build instead.
+  codesign --force --sign "$SHANNONCOAT_SIGN_IDENTITY" \
+    --identifier "com.local.shannoncoat" "$APP" \
+    || { echo "error: signing with \"$SHANNONCOAT_SIGN_IDENTITY\" failed" >&2; exit 1; }
+else
+  codesign --force --sign - --identifier "com.local.shannoncoat" "$APP" >/dev/null 2>&1 \
+    || echo "warning: codesign failed; Accessibility permission may not stick" >&2
+fi
+
 touch "$APP"
 echo "Built: $APP"
 echo "Copy it to /Applications (or ~/Applications) to install."