feat(neogaia): declare a 2 GiB EFI system partition (task 0016)

Each generation stores a kernel and an initrd on the EFI system partition,
and this host runs a large third-party kernel, so 512 MiB holds only about
seven. An exhausted partition fails at bootloader installation, after the
build has already succeeded.

The partition cannot grow in place: it sits first on the disk with the
encrypted container immediately behind it, and an encrypted volume's start
offset cannot move without rewriting its whole payload. Only an install
applies this layout, so the change takes effect at the next reimage and
does nothing to the running machine until then.

Record that a flake only sees git-tracked files, which cost an evaluation
earlier, and correct the git identity gotcha that a hand-written gitconfig
had made false.

CLAUDE.md

@@ -29,9 +29,12 @@ The domain model (Host, Module, Skeleton, Auto-loader, Enable convention, overla
   Both were true only while the machine still ran CachyOS against a distro Nix daemon.
 - The substituters a `nix build` fetches from are the **daemon's** (`/etc/nix/nix.conf`), *not* the `nix.settings` of the config being built — those only govern the built system.
   The two coincide here because the dev host runs this flake; they diverge on any machine that does not.
-- Git identity is not configured anywhere yet — no `programs.git` in the flake and no `~/.gitconfig`, so `git commit` fails with "Author identity unknown".
-  History uses `alexion <contact@alexion.dev>`; pass it per-commit with `git -c user.name=… -c user.email=…` rather than writing config outside the flake.
+- Git identity is not declared in the flake — there is no `programs.git` — but commits do work: identity comes from a hand-written `~/.gitconfig` plus this checkout's `.git/config`.
+  Both sit outside the flake, so neither survives a reimage nor reaches another machine; history uses `alexion <contact@alexion.dev>`.
 - The primary build/verify seam for any Host is `nix flake check`, which builds `checks.x86_64-linux.<host>` (the system toplevel); cheap targeted checks use `nix eval .#nixosConfigurations.<host>.config...`.
+- A flake only sees **git-tracked** files, so a new file that has not been `git add`ed is invisible to evaluation even though it exists on disk.
+  The failure names the path and reads as if the file were missing: `error: Path 'secrets/shared.yaml' does not exist in Git repository`.
+  Staging is enough; the file need not be committed.
 - chaotic-nyx must **not** follow our `nixpkgs`, and its packages are built against chaotic's own pinned nixpkgs (its overlay defaults to `onTopOf = "flake-nixpkgs"`, the cache-friendly path).
   That is what lets the `nyx-cache.chaotic.cx` binary cache hit instead of compiling the CachyOS kernel from source; the tradeoff is that chaotic packages do not see our `unstable`/`stable` overlays.
 - The remote is self-hosted Gitea (`git.alexion.dev`), and the intended CLI is `gitea-axi` rather than `tea`.