chore: 清除 zsh 残留，声明式 git 身份与 SSH config

- 移除所有 zsh 引用，补全 fish 迁移
- git.nix: 声明 userName/userEmail，删除 credential.helper store 和内网 sslVerify
- 新增 programs.ssh 声明式配置（id_ed25519, addKeysToAgent）
- 简化 install.sh 为 darwin/nixos 双平台

home/dev/git.nix

@@ -3,10 +3,8 @@
 {
   programs.git = {
     enable = true;
-
-    # user.name / user.email: set per-user via git config or ~/.zshrc.local
-    #   git config --global user.name "Your Name"
-    #   git config --global user.email "your@email.com"
+    userName = "imbytecat";
+    userEmail = "imbytecat@gmail.com";
 
     delta = {
       enable = true;
@@ -14,15 +12,10 @@
         navigate = true;
         side-by-side = true;
         line-numbers = true;
-        hyperlinks = true;
       };
     };
 
     extraConfig = {
-      # Internal Git server (skip SSL verification)
-      http."https://202.127.0.42:32443".sslVerify = false;
-
-      credential.helper = "store";
       merge.conflictstyle = "zdiff3";
       pull.rebase = true;
       push.autoSetupRemote = true;
@@ -33,7 +26,6 @@
     };
   };
 
-  # ── Lazygit ──────────────────────────────────────────
   programs.lazygit = {
     enable = true;
     settings = {
@@ -41,19 +33,20 @@
         nerdFontsVersion = "3";
         showBottomLine = false;
       };
-      git.paging = {
-        pager = "delta --paging=never";
-      };
+      git.paging.pager = "delta --paging=never";
       update.method = "never";
       disableStartupPopups = true;
     };
   };
 
-  # ── GitHub CLI ───────────────────────────────────────
   programs.gh = {
     enable = true;
-    settings = {
-      git_protocol = "ssh";
-    };
+    settings.git_protocol = "ssh";
+  };
+
+  programs.ssh = {
+    enable = true;
+    addKeysToAgent = "yes";
+    matchBlocks."*".identityFile = "~/.ssh/id_ed25519";
   };
 }