ci(test): key mise-action's tool cache on mise.lock and raise mise's HTTP retries

.github/workflows/test.yml

@@ -33,11 +33,23 @@ jobs:
 
       - name: Set up mise
         uses: jdx/mise-action@1648a7812b9aeae629881980618f079932869151 # v4.0.1
+        env:
+          # mise retries a failed download 3 times, with 2.6 to 5.2 s of backoff in total. 6 retries give 25 to 50 s.
+          MISE_HTTP_RETRIES: "6"
         with:
           # --locked installs only tools listed in mise.lock, fails when an entry is missing, and never rewrites it.
           # Without it, `mise install` fills in missing lock data and downloads tools again to do it, so a slow
           # www.lua.org failed this step.
           install_args: --locked
+          # The default cache key hashes every mise config file, so an edit to a task in mise.toml missed the cache and
+          # every tool downloaded again. mise.lock pins the tool set, so this key hashes only it. There are no
+          # restore-keys on purpose: mise does not check an installed tool against mise.lock, so a cache restored from
+          # another lock could keep a tool that the new lock changed. A change that alters an install without changing
+          # mise.lock (a tool option in mise.toml) keeps this key: bump v1 then.
+          cache_key: mise-v1-{{platform}}-{{version}}-${{ hashFiles('mise.lock') }}
+          # Only a push to main saves the cache. A pull request only restores it: mise runs the postinstall hooks of the
+          # PR's own mise.toml before the save, and the key above ignores mise.toml.
+          cache_save: ${{ github.event_name == 'push' }}
           # mise is pinned because `--locked` rules change between releases (2026.11.0 started to require a
           # checksum). sha256 is the linux-x64 mise binary from the v2026.11.5 release.
           version: 2026.11.5