Record the freshness token observed AFTER the read (re-stat post-read, falling
back to the routing stat if the file vanished) so the version returned/recorded
matches the bytes returned — a writer racing between the routing stat and the
read can no longer make a follow-up edit spuriously stale. Stream reads when the
backend reports no size, so a size-less backend never buffers a large file
whole. Update the cordis-catalog link map to the current filesystem API symbols
(FileContextExec/FileReadRequest/FileReadOutcome/FsInfo/FsWriteExpectation).
Implements the split-the-filesystem-seam RFC. ctx.fs shrinks to a text-storage
provider seam (resolve/stat/readText/streamText/writeText/editText with branded
FsTargetKey/FsVersion and an explicit FsWriteExpectation); the new
dsh-file-context package owns the model-facing policy (read windowing,
observed-state, write/edit freshness) as the concrete ctx.fileContext service.
Authorization is now freshness-based rather than full/partial view: a windowed
read records the file version and authorizes a later edit when the file is
unchanged, removing the dead-end where reading lines 100-150 of a large file
could not edit line 120. editText stays a provider primitive so version guard +
literal match + atomic rewrite remain one critical section, and the stale check
runs before matching so a stale edit reports FS_STALE_VERSION. tool-fs injects
fileContext, never reaching around to ctx.fs (the no-bypass contract).
Dudu-0223