fix cxxmodule: export all CPOs unconditionally in fast_io module wrapper

[SekaiArendelle]

fix(cxxmodule): export all CPOs unconditionally in fast_io module wrapper Several customization point objects (io_stream_ref_define, output_stream_ref_define, write_some_overflow_define, etc.) in cxxmodule/fast_io/fast_io_inc/core.inc were guarded by #if !defined(clang), under the assumption that clang supports finding non-exported names via ADL in module contexts. This assumption does not hold on clang 23 for x86_64-windows-gnu, where importing the fast_io module and calling println(u8c_stdout(), u8string) fails: static assertion failed due to requirement 'type_ok': some types are not printable for print on default C's stdout Without these exports, the requires clause on output_stream_ref (has_output_or_io_stream_ref_define) fails via SFINAE, causing print_freestanding_okay to fall through to the char-based hosted path, which cannot handle char8_t data. Remove the clang guard so CPOs are exported unconditionally. Also prefix all HTML AST node types with Html in pltxt2htm.cppm to match the upstream rename, and add missing table-node exports.

[SekaiArendelle]

Minimal reproduction for fast_io C++20 module CPO export issue on clang

Issue

When using fast_io as a C++20 module on clang (tested on clang 23 for
x86_64-windows-gnu, but likely affects other clang versions/targets too),
printing a u8string to u8c_stdout() fails:

error: static assertion failed due to requirement 'type_ok':
some types are not printable for print on default C's stdout

The static_assert is in fast_io_legacy_impl/io.h:91.

Root Cause

In cxxmodule/fast_io/fast_io_inc/core.inc (and other .inc files),
several customization point objects (CPOs) are guarded by
#if !defined(__clang__):

#if !defined(__clang__) // The gcc and msvc module does not support
                        // non-exported functions adl matching
using ::fast_io::io_stream_ref_define;
using ::fast_io::output_stream_ref_define;
using ::fast_io::write_some_overflow_define;
// ... many more CPOs ...
#endif

The comment assumes clang supports ADL matching non-exported names in
module contexts, so these exports are skipped for clang.

However, on clang 23 for x86_64-windows-gnu, this assumption is wrong.
Without these explicit using exports, the CPOs are not reachable from
importing TUs, so:

1. println(u8c_stdout(), u8string) checks
   print_freestanding_okay<u8c_stdout_type, u8string>
2. This calls output_stream_ref(declval<u8c_stdout_type>())
3. output_stream_ref has a requires clause
   has_output_or_io_stream_ref_define<T> which needs ADL to find
   io_stream_ref_define
4. ADL fails → output_stream_ref is not viable → the concept fails
5. Falls through to the char-based hosted path
6. print_freestanding_params_okay<char, u8string> fails because
   char != char8_t → static_assert

Fix

Remove the #if !defined(__clang__) guard or add a version check so
that all CPOs are unconditionally exported:

// Before:
#if !defined(__clang__)
using ::fast_io::io_stream_ref_define;
// ...
#endif

// After (unconditional export):
using ::fast_io::io_stream_ref_define;
// ...

Files to fix

• cxxmodule/fast_io/fast_io_inc/core.inc — the largest block of CPO
  exports guarded by #if !defined(__clang__)
• cxxmodule/fast_io/fast_io_inc/legacy/c.inc — line 39–41:
  pread_some_bytes_underflow_define, pwrite_some_bytes_overflow_define
• cxxmodule/fast_io/fast_io_inc/device.inc — various write_some_*
  and read_some_* CPOs

Tested Environment

• OS: Windows (x86_64)
• Compiler: clang 23.0.0git
  (target: x86_64-unknown-windows-gnu)
• Build system: CMake 3.28+ with Ninja
• C++ Standard: C++23

[SekaiArendelle]

Based on https://eel.is/c++draft/basic.lookup.argdep:

Argument-dependent lookup finds all declarations of functions and function templates that …
are exported, are attached to a named module M, do not appear in the translation unit containing the point of the lookup, and have the same innermost enclosing non-inline namespace scope as a declaration of an associated entity attached to M.