refactor,feat(emacs): Refactor emacs.nix

- Added Tree-sitter grammars.
- Attempting to do so led to discovering how janky the previous setup was.
- Previous package "bootstrapping" process looked like

    emacsPackage (The selected Emacs build from Nixpkgs)
         ↓
    emacs-wrapper (My wrapper that set envvars and included external deps)
         ↓
    programs.emacs.finalPackage (The package created by the HM module, which
                                 included Nix-managed Emacs packages)

  Now, we have

    emacsBasePackage (The selected build from Nixpkgs)
         ↓
    my-emacs (My wrapper that manages envvars, external packages, Nix-managed
              Emacs packages, and everything else)
   
  `programs.emacs.finalPackage` still exists, but it doesn't do anything that
  `my-emacs` doesn't.

users/crumb/programs/emacs.nix

@@ -1,11 +1,7 @@
 { config, lib, pkgs, inputs, ... }@args:
 
-# NOTE: Remember to wrap `programs.emacs.finalPackage` rather than pass a
-# wrapped package to `programs.emacs.package`, lest some unexpected behaviour
-# occur when home-manager calls emacs during the build process.
-
 let
-  emacsPackage = pkgs.emacs30-pgtk;
+  emacsBasePackage = pkgs.emacs30-pgtk;
   emacsConfigDir = "/persist/dots/users/crumb/programs/emacs";
 
   emacs-overlay =
@@ -41,10 +37,16 @@ let
       en en-computers en-science
     ]);
 
-  emacsWrapper =
-    pkgs.symlinkJoin {
-      name = "emacs-wrapper";
-      paths = [ emacsPackage ];
+  my-emacs =
+    let ewp = (pkgs.emacsPackagesFor emacsBasePackage).emacsWithPackages
+      (epkgs: with epkgs; [
+        jinx
+        pdf-tools
+        treesit-grammars.with-all-grammars
+      ]);
+    in pkgs.symlinkJoin {
+      name = "sydmacs";
+      paths = [ ewp ];
       nativeBuildInputs = [ pkgs.makeWrapper ];
       buildInputs = [
         pkgs.git # Dependency of Straight.el.
@@ -52,36 +54,34 @@ let
         pkgs.direnv
       ];
       postBuild = ''
-        # The binary called `emacs` is actually a symlink to `emacs-«version»`, so
-        # we needn't wrap it.
-        for i in $out/bin/emacs-*; do
-          wrapProgram "$i" \
-            --add-flags "--init-directory \"${emacsConfigDir}\"" \
-            --set EMACS_STRAIGHT_BASE_DIR "${straightBaseDir}" \
-            --set EMACS_CACHE_DIR "${emacsCacheDir}" \
-            --set EMACS_DATA_DIR "${emacsDataDir}" \
-            --prefix PATH : "${pkgs.git}/bin" \
-            --prefix PATH : "${my-aspell}/bin" \
-            --prefix PATH : "${pkgs.direnv}/bin" \
-            --prefix PATH : "${pkgs.texliveFull}/bin" \
-            --set ASPELL_CONF "dict-dir ${my-aspell}/lib/aspell"
-        done
+        # We specify `-type f` because `emacs` is sometimes a symlink to
+        # `emacs-«version»`.  If we were to wrap the symlink, Emacs would be
+        # wrapped *twice*.
+        find "$out" -type f -name emacs -or -name "emacs-*" \
+          | while IFS= read -r emacs; do
+              wrapProgram "$emacs" \
+                --add-flags "--init-directory \"${emacsConfigDir}\"" \
+                --set EMACS_STRAIGHT_BASE_DIR "${straightBaseDir}" \
+                --set EMACS_CACHE_DIR "${emacsCacheDir}" \
+                --set EMACS_DATA_DIR "${emacsDataDir}" \
+                --prefix PATH : "${pkgs.git}/bin" \
+                --prefix PATH : "${my-aspell}/bin" \
+                --prefix PATH : "${pkgs.direnv}/bin" \
+                --prefix PATH : "${pkgs.texliveFull}/bin" \
+                --set ASPELL_CONF "dict-dir ${my-aspell}/lib/aspell"
+          done
       '';
-      meta = emacsPackage.meta;
-      version = emacsPackage.version;
+      meta = emacsBasePackage.meta;
+      version = emacsBasePackage.version;
     };
 
   emacsclient-or-emacs = pkgs.writeShellScriptBin "emacsclient-or-emacs" ''
-    emacsclient --alternate-editor=${emacsWrapper}/bin/emacs "$@"
+    emacsclient --alternate-editor=${config.programs.emacs.finalPackage}/bin/emacs "$@"
   '';
 in {
   programs.emacs = {
     enable = true;
-    package = emacsWrapper;
-    extraPackages = epkgs: [
-      epkgs.jinx
-      epkgs.pdf-tools
-    ];
+    package = my-emacs;
   };
 
   sydnix.impermanence.cache.directories =