refactor: reduce complexity of execute_impl in assign_github_issue_milestone.rs

[github-actions]

Summary

Clippy's too_many_lines lint flagged AssignGithubIssueMilestoneResult::execute_impl at 166/100 lines. The function mixed request validation, GitHub API target/filter checks, numeric-vs-title milestone resolution (including auto-create), and the final PATCH assignment all in one body, with a large nested if/else for the two milestone-resolution paths.

Change

Extracted two pure/async helper functions to isolate the milestone-resolution logic, each returning Result<Result<ResolvedMilestone, ExecutionResult>> so the caller can propagate soft failures without inline branching:

• resolve_milestone_by_number — looks up an explicit milestone_number against the fetched milestone list and checks the allow-list policy.
• resolve_milestone_by_title — matches an existing milestone by title, disambiguates duplicates, and auto-creates a milestone when allowed and none matches.

execute_impl now delegates to whichever helper matches the request shape and unwraps the Result in a single early-return, keeping the top-level function focused on target validation, GitHub client setup, and the final assignment PATCH.

No public API, behavior, or error messages were changed — all logic/text branches were moved verbatim into the new helpers.

Verification

• cargo build — clean.
• cargo test --bin ado-aw safe_outputs::assign_github_issue_milestone — all 6 existing tests pass.
• cargo clippy --all-targets --all-features -- -W clippy::too_many_lines — no more warning for this file/function.

Generated by Cyclomatic Complexity Reducer · auto · 87.4 AIC · ⌖ 11.7 AIC · ⊞ 11.4K · ◷

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