FABRIC-3 XLVIII.10: retire v3, ruled for alpha.5 (#156); #155 filed [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

@@ -6366,3 +6366,18 @@ Plan `2026-10-29-stick-5`, Task 2; `STICK.md` 5a (its 2 TiB cap amended to 256 G
   Recommended: flush and read only the BAM pages that hold a volume's user blocks (the same bytes
   on disk, v3's behaviour unchanged); it is shared v3 code, so it waits for Captain Bob.
 
+
+### 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.
+- **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.
+- **My calls, open to a ruling when alpha.5 starts** (no preference given): tag the tree first
+  (`archive/v3-final`); the block layer to `v4/storage/`; `proof/` (all 52 theories are of the v3
+  VM) archived under the tag and removed with the nightly `proofs` stage; the v3-only features --
+  the fleet, the word ACL, MINT/WIREBIND, the DoE runtime -- go with v3, their designs kept here and
+  in the tag, for v4 to rebuild.
+- **Also filed** (#155, alpha.4, for a ruling): a block flush rewrites the whole BAM, 24 MiB each way
+  now that the stick's BAM is sized for 256 GiB (section 9).