The staleness fix (f9b1fd799) bolted two wall-clock dicts (_changed_at,
_pulled_at) onto a client that already scattered per-document state
across six parallel dicts (_files, _push_diagnostics, _pull_diagnostics,
_published, _published_version, _first_push_seen) — eight maps kept in
sync by hand.
Collapse all of it into one _DocState per path, and use the LSP document
version as the freshness token instead of clocks:
- didChange bumps doc.version; stored push/pull results carry the
version they describe (push_version from the server's echoed version,
or the current version at receipt for servers that don't echo one;
pull_version captured at request send so an in-flight pull that a
didChange races past is stale on arrival).
- fresh == tag >= version. Invalidation is implicit in the bump — no
store-clearing, no clock comparisons, no race windows.
- _has_fresh_push/_has_fresh_pull helpers dissolve into two one-line
_DocState methods; diagnostics_for(fresh_only=True) becomes a
three-liner.
Semantics are unchanged from f9b1fd799 (same tests pass, one test
updated off private internals); net -15 lines.
eb09df6ec8