interop: secsgem-py cross-validation harness + lenient identifier parsing

Adds a Docker-based interop harness that drives the C++ server with
secsgem-py 0.3.0 as the active host and probes a secsgem-py-passive
equipment from a minimal C++ active client.  Surfaces and fixes four
interoperability bugs uncovered by cross-testing:

  * SEMI E5 identifier formatcodes are a U1|U2|U4|U8 wildcard;
    secsgem-py picks the narrowest fitting width while our parsers
    only accepted U4.  `as_uN_scalar` / `as_iN_scalar` now accept
    any unsigned/signed width and range-check the downcast.
  * PPBODY (S7F3/F6) is "ASCII | Binary | List" per the spec;
    secsgem-py defaults to ASCII.  Added BINARY_OR_ASCII codegen
    item type with `as_text_or_binary` accessor.
  * S1F23/F24 Collection Event Namelist was unimplemented; added
    schema + `vids_for(ceid)` accessor on EventReportSubscriptions
    plus the dispatch handler.
  * S10F1 was registered as a host->equipment handler, but per
    SEMI E5 §12 S10F1 is equipment->host; S10F3 is the actual
    host->equipment Terminal Display Single.  Added an S10F3
    handler alongside (we keep S10F1 too for backward compat).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tools/gen_messages.py

@@ -49,6 +49,12 @@ SCALAR_TABLE = {
                      "as_binary_first({i})"),
     "BINARY":       ("std::string", "secs2::Item::binary(std::vector<uint8_t>({v}.begin(), {v}.end()))",
                      "as_binary_string({i})"),
+    # SEMI's "ASCII | Binary" wildcard (e.g. PPBODY).  Sent as Binary,
+    # accepted as either Binary or ASCII (JIS-8 too) so we interoperate
+    # with libraries like secsgem-py that default to ASCII.
+    "BINARY_OR_ASCII": ("std::string",
+                         "secs2::Item::binary(std::vector<uint8_t>({v}.begin(), {v}.end()))",
+                         "as_text_or_binary({i})"),
     "BOOLEAN":      ("bool",        "secs2::Item::boolean({v})",
                      "as_boolean({i})"),
     "ITEM":         ("secs2::Item", "{v}",