fix(mex): unblock multi-platform auto-PR pipeline (2 bugs)

.github/workflows/refresh-mex-binaries.yml

@@ -259,13 +259,20 @@ jobs:
     steps:
       - uses: actions/checkout@v6
 
-      # Download ALL artifacts into the workspace; merge-multiple preserves
-      # the repo-relative paths each artifact was uploaded with, dropping
-      # them back into libs/.../{,octave-<tag>/}.
+      # Download ALL artifacts and overlay them onto libs/.
+      # IMPORTANT: actions/upload-artifact trims the least-common-ancestor of
+      # the supplied paths, so each artifact's internal root is `FastSense/`
+      # (or `SensorThreshold/`) — NOT `libs/FastSense/`. We MUST set
+      # `path: libs` here so merge-multiple extracts under libs/, not the
+      # workspace root. Without `path: libs`, files land at workspace
+      # `FastSense/.../*.mex*`, the aggregator's `find libs` step sees
+      # nothing new, create-pull-request finds no diff, and the auto-PR
+      # silently fails to open.
       - uses: actions/download-artifact@v8
         with:
           pattern: mex-*
           merge-multiple: true
+          path: libs
 
       - name: Regenerate .mex-version stamp
         shell: bash

install.m

@@ -126,12 +126,24 @@
     % NOT yet on path (e.g., when __probe_needs_build__ is called after a
     % fresh addpath in the shim but before the candidates loop would run).
     octTag = get_octave_platform_tag();
+    isOctave = exist('OCTAVE_VERSION', 'builtin');
     probes = {
         fullfile(mex_dir, ['binary_search_mex.' mexext()])
-        fullfile(mex_dir, 'binary_search_mex.mex')
     };
-    if ~isempty(octTag)
-        probes{end+1} = fullfile(mex_dir, ['octave-' octTag], 'binary_search_mex.mex');
+    if isOctave
+        % On Octave, mexext() may be 'mex' already (covered by probe 1
+        % above) but legacy installs may also have a bare .mex file —
+        % keep that as a fallback. On MATLAB this probe is dangerous:
+        % stale Octave .mex files from before the octave-<tag>/ subdir
+        % convention sit alongside platform-specific binaries and
+        % falsely satisfy the "MEX present" check, causing
+        % FASTSENSE_SKIP_BUILD-like behaviour and an empty release
+        % artifact on platforms with no committed binary (e.g.
+        % Windows MATLAB).
+        probes{end+1} = fullfile(mex_dir, 'binary_search_mex.mex');
+        if ~isempty(octTag)
+            probes{end+1} = fullfile(mex_dir, ['octave-' octTag], 'binary_search_mex.mex');
+        end
     end
     core_ok = false;
     for pi = 1:numel(probes)