The shared code-language table must not claim a suffix a dedicated viewer
declares, and the Host read card must keep the `lang` values it already
persisted.
- Drop `csv` from the shared table: Code registers before Spreadsheet, so
the earlier body would take `.csv` and the browser snapshot gate fails.
- Add `readLangHintForPath`, the read card's legacy projection over the
shared table: the 43 pre-unification suffixes keep their old short ids
byte for byte, new suffixes use the canonical id.
- Add an ownership regression test over the full preview registry that
turns red when `csv` returns, plus byte-level and alias-normalized tests
for the read projection.
The document Code preview and the Host read card each owned an
extension-to-language table that had drifted: the preview table had 13
extensions the read card lacked, and the two returned different language
ids for the same suffix. Both now resolve through the new zero-dependency
@deepseek-ai/dsh-util-code-language, which also adds common Windows,
config, markup, and language extensions. Every added grammar stays in the
lazy set; the boot grammars are unchanged.
Fixes#4822
mektpoy