Add Gitea Actions Runner and update OpenCode config

- Add Gitea Actions Runner service on m3-atlas with nixos:host label
- Configure agenix secret for runner token
- Add Antigravity provider models to OpenCode config
- Switch m3ta-nixpkgs to local path for development

flake.lock

@@ -24,11 +24,11 @@
     "agents": {
       "flake": false,
       "locked": {
-        "lastModified": 1767965833,
-        "narHash": "sha256-8tKEfJU4bxlgPJwUTUDQkVJMbwWQMiYt+moLjMIFeVY=",
+        "lastModified": 1768312204,
+        "narHash": "sha256-wB1pEROaXzJzxCaJwOyXmD0gq8/hv7OeEw3jNXrPwAc=",
         "ref": "refs/heads/master",
-        "rev": "3e20c82603a4ddedf04ff001adf943723a49dc37",
-        "revCount": 7,
+        "rev": "cfa0f8f942545434a825fedf0a49061d26fff73d",
+        "revCount": 9,
         "type": "git",
         "url": "https://code.m3ta.dev/m3tam3re/AGENTS"
       },
@@ -243,8 +243,8 @@
         "nixpkgs": "nixpkgs_3"
       },
       "locked": {
-        "lastModified": 1768245745,
-        "narHash": "sha256-CHspl0D+ougqFToY6d0ZQk5KtNfCyB8AWnmeVWkuuRk=",
+        "lastModified": 1768419432,
+        "narHash": "sha256-EwJZcXCEF1ExSfZP4asi1ATOhj1xcvH3tIe5nDSk9Oc=",
         "path": "/home/m3tam3re/p/NIX/nixpkgs",
         "type": "path"
       },
@@ -435,11 +435,11 @@
     },
     "nixpkgs_3": {
       "locked": {
-        "lastModified": 1766309749,
-        "narHash": "sha256-3xY8CZ4rSnQ0NqGhMKAy5vgC+2IVK0NoVEzDoOh4DA4=",
+        "lastModified": 1768127708,
+        "narHash": "sha256-1Sm77VfZh3mU0F5OqKABNLWxOuDeHIlcFjsXeeiPazs=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "a6531044f6d0bef691ea18d4d4ce44d0daa6e816",
+        "rev": "ffbc9f8cbaacfb331b6017d5a5abb21a492c9a38",
         "type": "github"
       },
       "original": {