docs: FABRIC-3 XLVIII.18 -- a clean tree for alpha.5; README: alpha.4 is a release

XLVIII.18 records 2026-11-11: the LFS trim (Captain Bob: "they can be
trimmed out"), version.h untracked and BLOCK_MAP.md without its timestamp
(#145), my put-back error and its fix, the acceptance rulings (never in the
background; all logs and CSVs are evidence), the acceptance of 9415d7ed,
and alpha.4's Gitea release marked final.

README: alpha.4's release is no longer a pre-release.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017RzZgrf7V7Zk2iczBXDRbm

README.md

@@ -7,7 +7,7 @@ runs StarForth as its sole userspace runtime. No libc. No OS. Just stone and nec
 
 **Try it in your browser:** [starshipos-f18.com](https://starshipos-f18.com/) — a StarshipOS
 machine of your own, booted to `[zuse@Hera] ok>`, thrown away when you leave. **Releases:**
-[v4.0.0-alpha.4](https://gitea.starshipos-f18.org/rajames/LithosAnanke/releases) (pre-release),
+[v4.0.0-alpha.4](https://gitea.starshipos-f18.org/rajames/LithosAnanke/releases),
 the kernel `4.0.0-alpha.4` with the StarForth engine `3.2.0`.
 
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