ci(release): rename brew token env var and add conditional upload

The environment variable for the Homebrew tap token has been renamed from
HOMEBREW_TAP_GITHUB_TOKEN to GH_PAT to simplify naming. Additionally,
conditional upload logic has been added to the brew configuration to skip
upload when the token is not set, preventing release failures in environments
where the token is unavailable.

Author: zzxwill

.github/workflows/release.yml

@@ -30,4 +30,4 @@ jobs:
           args: release --clean
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          HOMEBREW_TAP_GITHUB_TOKEN: ${{ secrets.GH_PAT }}
+          GH_PAT: ${{ secrets.GH_PAT }}

.goreleaser.yml

@@ -66,10 +66,11 @@ release:
 
 brews:
   - name: agentx
+    skip_upload: "{{ if .Env.GH_PAT }}false{{ else }}true{{ end }}"
     repository:
       owner: agentsdance
       name: agentx
-      token: "{{ .Env.HOMEBREW_TAP_GITHUB_TOKEN }}"
+      token: "{{ .Env.GH_PAT }}"
     directory: Formula
     homepage: "https://github.com/agentsdance/agentx"
     description: "CLI tool for managing MCP servers and skills across AI coding agents"