refactor(api)!: one way to ask what a file is

[andiwand]

🤖 Generated with Claude Code

PR 5 of the v7 API plan.

Twelve public entry points answered what is this file. This leaves four —
two questions over two input types.

The four duplicate statics

DecodedFile::list_file_types and DecodedFile::mimetype (×2 each) were the
implementation; odr::list_file_types and odr::mimetype were one-line
forwards to them. The bodies move up to the free functions and the statics go.

The clearest evidence this was a real fork and not a harmless alias: the
bindings picked different ones. apple/src/ODRFile.mm called
odr::DecodedFile::list_file_types, jni/src/jni_core.cpp called
odr::list_file_types, for the same operation.

DocumentFile::type and ::meta

FileType DocumentFile::type(const File &file) {
  return DocumentFile(file).file_type();   // decodes the whole file
}

Four statics that decoded an entire document to read one field, and threw
NoDocumentFile for anything that was not a document — so type(some.png) was
an exception rather than FileType::portable_network_graphics.
open(...).file_type() and .file_meta() answer without the narrowing.

Bindings

	gone
Java	DocumentFile.typeByPath, DocumentFile.metaByPath
Python	DocumentFile.type_by_file / type_by_path / meta_by_file / meta_by_path
ObjC	unchanged surface; listFileTypes/mimetype now call the free functions

The python binding's own comment is a small monument to the problem it had —
"type/meta are overloaded on File and path, so the address of either is
ambiguous; name the signature" — four def_statics existing to disambiguate
an overload set that did not need to exist.

Tests

FileTest.documentFileByPath tested the removed statics; rewritten to assert
what it was actually after, that a path names an odt, through
Odr.open(path).fileType() / .fileMeta(). test_file.py's two cases
likewise.

Net −131/+39.

Verified

Full build clean. 222 gtests (File*, *Csv*, *Markdown*, *Xml*,
*Flat*, *Document*), 69 python tests, JNI junit via ctest --test-dir jni
— all pass.

Migration

DecodedFile::mimetype(path)        →  odr::mimetype(path)
DecodedFile::list_file_types(path) →  odr::list_file_types(path)
DocumentFile::type(path)           →  odr::open(path).file_type()
DocumentFile::meta(path)           →  odr::open(path).file_meta()