L5: dock-panel button refinements — overflow menu, tooltips, opposite-mode tag buttons

Top-bar rare-capture variants move to a right-anchored More popup; short faces gain
hover-delay full-name tooltips (prefix stripped); bottom bar becomes four opposite-mode
Item/Track tag buttons + Show Both (Toggle/Activates dropped); wider cluster gaps. New
pure overflow_menu/mode_enable/tooltip modules, CTest-covered. Same actions, same contract.

src/mode_enable.cpp

@@ -0,0 +1,21 @@
+// mode_enable — pure implementation. See mode_enable.h. NO REAPER / SWELL / LICE / vendor.
+
+#include "mode_enable.h"
+
+#include "view_mode_model.h"  // kArrangeModeId / kDesignModeId — the ONE home for the mode ids
+
+namespace reasampler {
+
+bool tagButtonEnabled(const std::string& activeModeId, TagTarget target) {
+    // The target's own mode id, so the rule is a single "target != active" compare.
+    const char* targetId =
+        (target == TagTarget::Arrange) ? kArrangeModeId : kDesignModeId;
+
+    // Fail-open on an unrecognized active id (neither seed mode): every button live, so a
+    // future added mode never dead-locks the bar and the user can always reach the action.
+    if (activeModeId != kArrangeModeId && activeModeId != kDesignModeId) return true;
+
+    return activeModeId != targetId;
+}
+
+} // namespace reasampler