feat(file): carry the name a file already has

[andiwand]

🤖 Generated with Claude Code

abstract::File knew where a file was but not what it was called. The name
was only reachable through disk_path, which a memory file does not have — so
file_type_by_name (#814) could offer markdown for a .md on disk and nothing
for the same bytes arriving from a download or a browser upload.

Core

• abstract::File::name(), and the public File::name(): the file's own name,
  without any directory.
  • DiskFile — the basename of its path.
  • MemoryFile — what it was constructed with, empty by default.
  • FileInZip / FileInCfb — the entry name.
• File::from_memory(std::string data, std::string name = {}) — the new second
  argument is how a caller with bytes and no path says what they were called.
  The default keeps every existing call site compiling and behaving as before.
• MemoryFile(const abstract::File &) takes the name along with the bytes, so
  reading a file off disk into memory does not forget it is about.odt.
• open_strategy::file_type_by_name reads the extension off name() rather
  than off disk_path(). A name still only ever adds a candidate the bytes
  already allow, and only for a type no content probe can produce (markdown,
  html) — so File::from_memory(md, "notes.md") now decodes as markdown, and a
  zip called notes.md is still a zip.

Bindings

	reads the name	names bytes
python	File.name()	File.from_memory(data, name="")
jni	File.name()	—
apple	File.name	—
wasm	Document.fileName	odr.open(bytes, { name }), odr.detect(bytes, name)

JNI and Apple never took bytes in the first place — their File is path-only —
so there is nothing to name there beyond what the path, or the archive entry,
already says. The wasm JS wrapper defaults the name, so no existing call
changes; wasm/README.md and the example page now pass the browser's
File.name, which is exactly the case the core change was for.

Testing

• gtest: File.name_is_the_file_name_on_disk,
  File.from_memory_is_unnamed_unless_told,
  File.a_file_read_into_memory_keeps_its_name,
  File.an_archive_entry_is_named_by_its_entry, and
  odr.a_named_file_in_memory_is_offered_its_type — bytes named notes.md
  list and open as markdown. Full odr_test: 1425 passed, 6 skipped (the same
  6 as on main).
• pytest 69 passed, JUnit 46 passed, node --test 38 passed, XCTest 26 passed —
  each including the new cases.
• The changed TUs re-checked with -Wall -Wextra -Wmissing-field-initializers -Werror -fsyntax-only (emscripten's clang for the wasm one); clang-tidy
  reports only findings that pre-date this change.