chore(flake): refresh nixpkgs inputs to 2026-09-11

Bump nixpkgs and nixpkgs-latest from 2026-05/2026-08 to current
nixos-unstable (2026-09-11); both inputs now resolve to the same rev.
Re-validated every package against the new inputs.

Fallout fixed:
- freetoken: upstream pins torch>=2.11,<2.12 and triton==3.6.0, but the new
  nixpkgs only ships torch 2.13 / triton 3.7. Add a nixpkgs-torch211 input
  pinned at the previous revision and build freetoken against it, keeping
  the CUDA 12.9 / torch 2.11 stack unchanged.
- graphify: nixpkgs' pybloomfilter3 0.7.3 ships sdist metadata that still
  says 0.7.2, tripping pythonMetadataCheckPhase; skip that check only.

All 22 packages build and `nix flake check --no-build` passes.

flake.lock

@@ -75,11 +75,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1777954456,
-        "narHash": "sha256-hGdgeU2Nk87RAuZyYjyDjFL6LK7dAZN5RE9+hrDTkDU=",
+        "lastModified": 1789149629,
+        "narHash": "sha256-H6GwaZzZf+4npqv0tph94w9tZddSjFjmQrVsW0z78uk=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "549bd84d6279f9852cae6225e372cc67fb91a4c1",
+        "rev": "eaad089433ca2bb662274377d33df3d0e51ef28b",
         "type": "github"
       },
       "original": {
@@ -91,11 +91,11 @@
     },
     "nixpkgs-latest": {
       "locked": {
-        "lastModified": 1785967620,
-        "narHash": "sha256-IItrdb7Puk05RqOBWZYFC5X6Wl1sJmCfh5MWVHw5iMM=",
+        "lastModified": 1789149629,
+        "narHash": "sha256-H6GwaZzZf+4npqv0tph94w9tZddSjFjmQrVsW0z78uk=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "b7c2ada94fe99c15b0dbcf4d11fd7850b957a436",
+        "rev": "eaad089433ca2bb662274377d33df3d0e51ef28b",
         "type": "github"
       },
       "original": {
@@ -105,6 +105,22 @@
         "type": "github"
       }
     },
+    "nixpkgs-torch211": {
+      "locked": {
+        "lastModified": 1777954456,
+        "narHash": "sha256-hGdgeU2Nk87RAuZyYjyDjFL6LK7dAZN5RE9+hrDTkDU=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "549bd84d6279f9852cae6225e372cc67fb91a4c1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "549bd84d6279f9852cae6225e372cc67fb91a4c1",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "blueprint": "blueprint",
@@ -112,6 +128,7 @@
         "flake-parts": "flake-parts",
         "nixpkgs": "nixpkgs",
         "nixpkgs-latest": "nixpkgs-latest",
+        "nixpkgs-torch211": "nixpkgs-torch211",
         "systems": "systems",
         "treefmt-nix": "treefmt-nix"
       }