feat(branding): drop the nixpkgs codename — "Nomarchy 26.05", not "(Yarara)"

Yarara is nixpkgs' release name. Carrying it in PRETTY_NAME told users
something true about our upstream and nothing about our product, in the one
string every fetch tool and greeter reads.

Upstream hardcodes the codename into VERSION, PRETTY_NAME and
VERSION_CODENAME (misc/version.nix) with no switch, and
`system.nixos.codeName = ""` is the wrong lever — it renders "26.05 ()".
So the assembled strings are overridden through the merge hooks upstream
does provide (extraOSReleaseArgs / extraLSBReleaseArgs), which is already
where our project URLs live. lsb-release gets the same treatment; it
carried the codename in three fields of its own.

Empty VERSION_CODENAME/DISTRIB_CODENAME is deliberate: `//` cannot remove a
key, os-release(5) makes every field optional, and the file already ships
ANSI_COLOR="" and IMAGE_ID="".

nixos-version still prints "(Yarara)" and is left alone on purpose: that
command reports which nixpkgs the system was built from — the one question
the codename actually answers. Reaching it would mean patching a nixpkgs
script for no gain.

Verified on the built system: PRETTY_NAME="Nomarchy 26.05", VERSION="26.05",
VERSION_ID="26.05"; lsb DISTRIB_DESCRIPTION="Nomarchy 26.05",
LSB_VERSION="26.05". fastfetch's os line reads PRETTY_NAME, so it follows.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/ROADMAP.md

@@ -555,6 +555,20 @@ Design/decision records and a running log of shipped work (items marked
   `%26`, `%3F`, `%23`, `caf%C3%A9`. **Unverified on purpose:** whether each
   vendor's page fills the box or auto-submits — testing that means posting into
   Bernardo's own accounts.
+- ✓ **No codename in the branding (2026-07-16):** Bernardo — the distro is
+  "Nomarchy 26.05", not "Nomarchy 26.05 (Yarara)". Yarara is *nixpkgs'* release
+  name; presenting it as ours told users something true about our upstream and
+  nothing about our product, in the one string (`PRETTY_NAME`) every fetch tool
+  and greeter reads. Upstream hardcodes the codename into `VERSION`,
+  `PRETTY_NAME` and `VERSION_CODENAME` (`misc/version.nix`) with no switch, and
+  `system.nixos.codeName = ""` is the wrong lever — it renders `26.05 ()`. So the
+  assembled strings are overridden through the merge hooks upstream does provide
+  (`extraOSReleaseArgs` / `extraLSBReleaseArgs`), which is also where our project
+  URLs already live. Empty `VERSION_CODENAME`/`DISTRIB_CODENAME` is deliberate:
+  `//` cannot remove a key, os-release(5) makes every field optional, and the
+  file already ships `ANSI_COLOR=""`. **`nixos-version` still prints "(Yarara)"
+  by design** — that command answers "which nixpkgs was this built from?", the
+  one question the codename genuinely answers.
 - ✓ **The #107 compat shim is pinned (#133, 2026-07-16):** `mkFlake` prefers
   `state.json` and still accepts the legacy `theme-state.json`, because a
   machine only migrates on its next menu write — but nothing evaluated a