FABRIC-3 XLVIII.10: retiring v3 is its own milestone (#156) [skip ci]

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GE3SDvQn5EoxdGufk84zz2

docs/fabric/FABRIC-3.md

@@ -6370,7 +6370,8 @@ Plan `2026-10-29-stick-5`, Task 2; `STICK.md` 5a (its 2 TiB cap amended to 256 G
 ### 10. Retire v3 (2026-11-08)
 
 - **Ruled** (Captain Bob): "v3 dependencies for v4 should be moved to v4 and the v3 code retired and
-  removed" -- in **alpha.5**, after #92 ships the plug-and-play stick in alpha.4. #156.
+  removed" -- after #92 ships the plug-and-play stick in alpha.4, as **its own milestone**, "Retire
+  v3" (first placed in alpha.5; then "That is its own milestone"). #156.
 - **What v4 takes from v3 today:** the block layer (`block_subsystem.c`, `blkio`, `log`, the
   platform time) and the `VM *` type in two kernel headers. The v4 engine includes nothing from v3;
   a v4 boot branches to `sk_v4_run()` before v3's VM is set up.