feat: flesh out work module and pin claude-code to nixpkgs unstable

Migrate git config to the settings option, fix the signing key path and email, add argo-rollouts/google-cloud-sdk and other tooling, enable go, and wire a dedicated nixpkgs-unstable input so claude-code tracks unstable independently of the pinned nixpkgs.

flake.lock

@@ -7,11 +7,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1747763032,
-        "narHash": "sha256-9j3oCbemeH7bTVXJ3pDWxOptbxDx2SdK1jY2AHpjQiw=",
+        "lastModified": 1780099287,
+        "narHash": "sha256-efIPwVGtIWIjWcznhaop6XN6HxnOL8800hF6CBNvlqQ=",
         "owner": "nix-community",
         "repo": "home-manager",
-        "rev": "29dda415f5b2178278283856c6f9f7b48a2a4353",
+        "rev": "7d8127d308c3fb9664f7e643eec944be74ebb37d",
         "type": "github"
       },
       "original": {
@@ -22,11 +22,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1747542820,
-        "narHash": "sha256-GaOZntlJ6gPPbbkTLjbd8BMWaDYafhuuYRNrxCGnPJw=",
+        "lastModified": 1779560665,
+        "narHash": "sha256-tpyBcxPpcQb8ukyNF7DoCwfSY3VPsxHoYwj00Cayv5o=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "292fa7d4f6519c074f0a50394dbbe69859bb6043",
+        "rev": "64c08a7ca051951c8eae34e3e3cb1e202fe36786",
         "type": "github"
       },
       "original": {
@@ -35,10 +35,27 @@
         "type": "indirect"
       }
     },
+    "nixpkgs-unstable": {
+      "locked": {
+        "lastModified": 1780243769,
+        "narHash": "sha256-x5UQuRsH3MqI0U9afaXSNqzTPSeZlRLvFAav2Ux1pNw=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "331800de5053fcebacf6813adb5db9c9dca22a0c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "home-manager": "home-manager",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "nixpkgs-unstable": "nixpkgs-unstable"
       }
     }
   },