runs-on names a machine, not a purpose

The purpose-prefixed labels (hanzo-build-*, hanzo-deploy-*, hanzo-docs-build-*)
are retired in favour of the bare <os>-<arch> every runner already advertises.

They were not a capability, only a habit, and the habit cost builds: papers asked
for hanzo-build-linux-amd64, no online runner offered it, and two idle
linux-amd64 runners sat beside the queue while the build simply never ran. The
lux tree lost three days to lux-linux-amd64 the same way.

What a job is FOR is the workflow's name. runs-on is the machine it needs.

.hanzo/workflows/deploy.yml

@@ -25,7 +25,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: [hanzo-build-linux-amd64]
+    runs-on: [linux-amd64]
     steps:
       - uses: actions/checkout@v4
 

.hanzo/workflows/e2e.yml

@@ -26,7 +26,7 @@ jobs:
   e2e_tests:
     name: 'E2E Tests'
     timeout-minutes: 60
-    runs-on: [hanzo-build-linux-amd64]
+    runs-on: [linux-amd64]
     steps:
       - uses: actions/checkout@v4