Merge #251 (fix/20ek-milr-rename-races, ff8ea239) into fix/8xq0-editor-commits-opened-record

OpenedCoordinate becomes #274's OpenedCell, now carrying #251's seen
(filled for a rename only) inside Opened::Target. Retry/Gone keep #251's
rename-only semantics in this commit; the value-cell retry (improvise-8phw)
follows. #221's superseded "a retry after a refusal is a force" paragraph
is dropped in favour of #251's rule.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze

context/code/protocol.md

@@ -662,7 +662,9 @@ operands come from the **projection**:
 
 `RenameRecordCoordinate` is position-free (improvise-hkbc): it names the record
 by surrogate and the new coordinate by value. `records_named` names the record,
-because a rename moves it (gotcha 43). Creating the item is internal to the
+because a rename moves it (gotcha 43). The destination, when it exists, is
+added by the server's `records_at_stake` rather than here, because only the
+document can derive it (improvise-milr, `context/code/command.md`). Creating the item is internal to the
 effect. `render.rs::editable` still answers `false` for a coordinate: the page's
 inline editor writes stored cells only, and the rename's producer is the
 keyboard path (`context/code/clients.md`). `typed_cell_command` and