test(deepseek): stop pinning Node's one-shot zstd decoder to the first frame

The frame-walking test asserted that zlib.zstdDecompressSync returns only the first of 40 concatenated frames. That was true when the walker was written, but nodejs/node#65865 (shipped in 26.10.0 and in 24.22.0 LTS) makes Node decode every frame, so the assertion fails on current Node 24 LTS and 26 while the walker itself is still correct. The assertion tested Node, not Codeman: the walker's own 40-frame checks stay, and the comments now say which Node versions stop at the first frame, since the supported range (>=22) still includes them.

docs/deepseek-integration.md

@@ -235,9 +235,10 @@ worker's first answer reads as an answer. Three things about the file shaped the
 reader (`src/deepseek-transcript.ts`):
 
 - **It is one zstd FRAME per append, not one zstd stream.** `zstd -dc` decodes all
-  of them, Node's `zlib` zstd decoder stops at the first: a real 56-line
-  transcript came back as 1 line. The reader walks frame headers itself. On a Node
-  older than 22.15 (no zstd at all) the mode falls back to the pane, as before.
+  of them, Node's `zlib` zstd decoder before 24.22 and 26.10 stops at the first:
+  a real 56-line transcript came back as 1 line. The reader walks frame headers
+  itself, which stays correct on a Node that decodes every frame
+  (nodejs/node#65865). On a Node older than 22.15 (no zstd at all) the mode falls back to the pane, as before.
 - **Not every `user/message` is the user.** Each turn also records a
   plugin-sourced runtime-context snapshot; only `source.kind === 'user'` is a
   prompt.