Create issue proposal for replacing go-github-mock with testify/mock

[Copilot]

Closes: N/A (this PR creates the issue proposal itself)

Creates a comprehensive issue proposal document at docs/issues/replace-go-github-mock.md to track the migration from migueleliasweb/go-github-mock to stretchr/testify/mock.

Scope analysis:

• 16 files using go-github-mock
• ~449 mock.NewMockedHTTPClient calls
• ~267 mock.WithRequestMatchHandler calls
• ~80+ unique endpoint patterns

Key proposal points:

• Consolidate testing deps (already using testify for assertions)
• Move from HTTP-level to interface-based mocking
• Compile-time type safety vs runtime matching
• githubv4mock for GraphQL remains unchanged (out of scope)

Tradeoffs:

• Created docs/issues/ directory to house issue proposals rather than using an existing location—this provides a clear home for future tracking documents.

Alternatives:

• Could have created a GitHub issue directly, but documenting in-repo allows the proposal to be reviewed and refined through the PR process before becoming an official issue.

Original prompt

Create an issue to replace migueleliasweb/go-github-mock with stretchr/testify

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