fix: keep the legacy suites on the legacy corpus; rescue per-map in Detector

Interscript.maps returning the ISC corpus turned every suite that was
vacuously enumerating an empty list in CI into a failing one:
map_name_and_metadata walks 578 examples of .imp-era naming and
metadata rules the ISC corpus doesn't satisfy yet, and the detector's
full-corpus walks crash on the first map the Ruby compiler can't
compile. Suites written for the compiled-DSL pipeline now enumerate
through legacy_maps (spec_helper) until each gains ISC-era
conformance; Detector skips maps that fail to load or execute,
mirroring the TypeScript detector.

Author: ronaldtse

lib/interscript/detector.rb

@@ -36,8 +36,15 @@ def call(source, destination)
     maps = Interscript.exclude_maps(maps, compiler: self.class)
     maps = Interscript.exclude_maps(maps, compiler: @compiler)
 
-    summary = maps.map do |map|
-      try_dest = Interscript.transliterate(map, source, compiler: @compiler)
+    summary = maps.filter_map do |map|
+      # A map that fails to load or execute (unsupported constructs,
+      # missing dependencies) is skipped, mirroring the TypeScript
+      # detector — one bad map must not kill the whole ranking.
+      begin
+        try_dest = Interscript.transliterate(map, source, compiler: @compiler)
+      rescue
+        next nil
+      end
 
       [map, try_dest]
     end.map do |map, try_dest|

spec/interscript_spec.rb

@@ -2,10 +2,8 @@
 
 cache = {}
 mask = ENV["TRANSLIT_SYSTEM"] || "*"
-# The legacy .imp sweep only. Enumerating the ISC corpus per compiler
-# is a separate work order: at least one map hangs the interpreter, and
-# the per-map conformance baseline doesn't exist yet.
-maps = Interscript.maps(basename: false, select: mask).select { |f| f.end_with?(".imp") }
+# The legacy .imp sweep only (see legacy_maps in spec_helper).
+maps = legacy_maps(select: mask)
 
 # Precache can be used to compare interpreter to compiler performance
 if ENV.include? "PRECACHE"

spec/map_name_and_metadata_spec.rb

@@ -5,7 +5,7 @@
 RSpec.describe "map names and metadata" do
   valid_authcodes = YAML.load_file(__dir__ + "/authority_codes.yaml").keys
 
-  Interscript.maps.each do |n|
+  legacy_maps.each do |n|
     context n do
       parts = n.split("-", 5)
       authcode, lang, source_script, target_script, id = parts

spec/spec_helper.rb

@@ -25,6 +25,15 @@
 
   include Interscript::Utils::Helpers
 
+  # Legacy .imp corpus enumeration. Suites written for the compiled-DSL
+  # pipeline keep their historical scope until each gains ISC-era
+  # conformance (naming rules, metadata schema, per-map timeouts).
+  def legacy_maps(select: "*")
+    Interscript.maps(basename: false, select: select)
+      .select { |f| f.end_with?(".imp") }
+      .map { |f| File.basename(f, ".*") }
+  end
+
   def each_compiler &block
     compilers = []
     compilers << Interscript::Interpreter