Problem: the file: token implementation had no test coverage.
Solution: add spec/file_spec.lua covering parse.body extraction,
malformed token handling, duplicate token stop-parsing, diff
reconciliation (store/update/clear/round-trip), LineMeta population
in both views, :Pending edit -file, and goto_file notify paths for
no-file and unreadable-file cases. All 292 tests pass.
