fix(build): exit 0 on a successful single-platform release

build.sh runs under `set -e`, and its final line was
`[[ -d release/mac ]] && echo …`. On a build that did not produce a mac
artifact (e.g. --win-release), the `[[ -d ]]` test is false; set -e exempts the
left side of an && so the script does not abort, but that non-zero status
becomes the script's exit code — making a fully successful build report failure
(and breaking CI status). Add an explicit `exit 0` at the end; real failures
already exit 1 at their point of failure.

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

build.sh

@@ -1306,3 +1306,9 @@ if $DO_LINUX || $DO_WIN || $DO_MAC; then
     [[ -d "$SCRIPT_DIR/release/windows" ]] && echo -e "    ${CYAN}windows/${NC}   — .exe + .zip"
     [[ -d "$SCRIPT_DIR/release/mac" ]]     && echo -e "    ${CYAN}mac/${NC}       — .app + .dmg"
 fi
+
+# Reaching here means the build completed (real failures exit 1 at their point of failure).
+# Exit 0 explicitly: the final `[[ -d release/mac ]] && echo` above returns non-zero on a
+# non-mac build — and since set -e exempts the left side of an &&, that status would otherwise
+# become the script's exit code and make a successful build report failure (e.g. to CI).
+exit 0