fix: correct cache key precedence to match runtime behavior

The cache key was preferring environment input over process.env.MISE_ENV,
but setEnvVars() does the opposite (existing MISE_ENV takes precedence).
This caused a cache key/runtime mismatch when both were set.

Now both use the same precedence: process.env.MISE_ENV || environment input

This ensures the cache key always matches the actual MISE_ENV value that
will be used at runtime.

Also corrected CHANGELOG.md to remove inaccurate statement about env input.

Fixes precedence inversion identified by Greptile review.

CHANGELOG.md

@@ -9,7 +9,7 @@
   - Simplifies multi-environment workflows by eliminating manual export step
   - Respects existing MISE_ENV environment variable (takes precedence)
   - Automatically included in cache key generation via {{mise_env}} template variable
-  - Only exports to GITHUB_ENV when `env` input is true (default)
+  - Exports to GITHUB_ENV making it available to all subsequent workflow steps
 
 ---
 ## [4.0.1](https://github.com/jdx/mise-action/compare/v4.0.0..v4.0.1) - 2026-03-22

dist/index.js

@@ -85189,10 +85189,10 @@ async function processCacheKeyTemplate(template) {
     const version = getInput('version');
     const installArgs = getInput('install_args');
     const cacheKeyPrefix = getInput('cache_key_prefix') || 'mise-v1';
-    // Check environment input first, then fall back to process.env.MISE_ENV
-    // This ensures the cache key includes the environment even before setEnvVars() runs
+    // Match the precedence in setEnvVars(): process.env.MISE_ENV takes precedence over environment input
+    // This ensures the cache key matches the runtime MISE_ENV value
     const environmentInput = getInput('environment');
-    const miseEnv = (environmentInput || process.env.MISE_ENV || '').replace(/,/g, '-');
+    const miseEnv = (process.env.MISE_ENV || environmentInput || '').replace(/,/g, '-');
     const platform = await getTarget();
     // Calculate file hash
     const fileHash = await hashFiles(MISE_CONFIG_FILE_PATTERNS.join('\n'));

src/index.ts

@@ -456,10 +456,10 @@ async function processCacheKeyTemplate(template: string): Promise<string> {
   const version = core.getInput('version')
   const installArgs = core.getInput('install_args')
   const cacheKeyPrefix = core.getInput('cache_key_prefix') || 'mise-v1'
-  // Check environment input first, then fall back to process.env.MISE_ENV
-  // This ensures the cache key includes the environment even before setEnvVars() runs
+  // Match the precedence in setEnvVars(): process.env.MISE_ENV takes precedence over environment input
+  // This ensures the cache key matches the runtime MISE_ENV value
   const environmentInput = core.getInput('environment')
-  const miseEnv = (environmentInput || process.env.MISE_ENV || '').replace(
+  const miseEnv = (process.env.MISE_ENV || environmentInput || '').replace(
     /,/g,
     '-'
   )