ci: move off self-hosted orion onto ubuntu-latest

.github/workflows/ci.yml

@@ -16,22 +16,14 @@ env:
 jobs:
   test:
     name: Test
-    # Self-hosted runner on orion.local (Apple M4 Pro, arm64). To fall back to
-    # GitHub-hosted, change this line to: runs-on: ubuntu-latest
-    runs-on: [self-hosted, orion]
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@d23441a48e516b6c34aea4fa41551a30e30af803 # v6.1.0
 
       - name: Setup Go
         uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
         with:
           go-version: '1.26'
-          # cache MUST stay false on the self-hosted orion runners: their
-          # filesystem persists between jobs, so ~/go/pkg/mod is already warm.
-          # setup-go's cache restore untars its archive over those files →
-          # "tar: Cannot open: File exists", failing the job in Setup Go before
-          # any code runs. Go reuses the on-disk module cache directly.
-          cache: false
 
       # Formatting gate (libs#30). Runs first because it's the cheapest check and
       # the fastest to act on. Nothing checked formatting before — this repo has

CHANGELOG.md

@@ -8,6 +8,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- CI moved off the self-hosted orion runner fleet onto `ubuntu-latest`. The
+  fleet (colima/Docker on orion.local) is being decommissioned org-wide; no
+  behavior change to the tool.
+
 ### Security
 - **Bumped `golang.org/x/text` v0.21.0 → v0.39.0 — CVE-2026-56852 (HIGH)** (#35).
   A `norm.Iter` can enter an infinite loop on certain input. libs only imports