Fix repoutil tests after repository org migration

[Copilot]

CI unit tests failing because pkg/repoutil test fixtures still referenced githubnext org after repository was moved to github org.

Changes

Updated test expectations in pkg/repoutil/repoutil_test.go:

• TestSplitRepoSlug - "githubnext" → "github"
• TestParseGitHubURL - "githubnext" → "github"
• TestSanitizeForFilename - "githubnext-gh-aw" → "github-gh-aw"

 {
   name:          "valid slug",
   slug:          "github/gh-aw",
-  expectedOwner: "githubnext",
+  expectedOwner: "github",
   expectedRepo:  "gh-aw",
   expectError:   false,
 },

Original prompt

Fix the failing GitHub Actions workflow test
Analyze the workflow logs, identify the root cause of the failure, and implement a fix.
Job ID: 62286209982
Job URL: https://github.com/github/gh-aw/actions/runs/21613163551/job/62286209982

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[Copilot]

Pull request overview

This PR fixes failing unit tests in pkg/repoutil after the repository was migrated from the githubnext organization to the github organization. The test fixtures were using outdated organization expectations that didn't match the repository's current location.

Changes:

• Updated test expectations in TestSplitRepoSlug to expect "github" instead of "githubnext"
• Updated test expectations in TestParseGitHubURL to expect "github" instead of "githubnext"
• Updated test expectations in TestSanitizeForFilename to expect "github-gh-aw" instead of "githubnext-gh-aw"

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