Add retry logic to create-team command for 5xx server errors

[Copilot]

Problem

The create-team command would fail permanently when encountering 5xx server errors (like HTTP 500 Internal Server Error) because the CLI doesn't retry write operations by default. This was causing integration test failures and user frustration when GitHub's API experienced temporary issues.

Example error from CI:

[2025-07-07 15:39:16] [ERROR] [HTTP ERROR 500] System.Net.Http.HttpRequestException: GitHub API error: 
 ---> System.Net.Http.HttpRequestException: Response status code does not indicate success: 500 (Internal Server Error).

Solution

Modified the GithubApi.CreateTeam() method to use the existing HttpRetry mechanism with intelligent idempotency checking:

1. Retry on 5xx errors: Uses HttpRetry with a filter for server errors (≥500)
2. Idempotency check: Before retrying, checks if the team was actually created despite the error response
3. Safe recovery: If team exists, returns the existing team details instead of attempting to create it again
4. Preserves existing behavior: 4xx client errors still don't retry (correct behavior)

Changes Made

• Modified GithubApi.CreateTeam(): Added retry logic with idempotency checking
• Added comprehensive tests:
  • Test retry on 500 error when team gets created
  • Test retry on 502 error with successful retry
  • Test that 400 errors don't trigger retries
• Updated release notes: Added user-friendly description of the fix

Testing

• All existing tests continue to pass (116 GithubApi tests)
• New tests verify retry behavior works correctly
• Integration with existing retry policy infrastructure

The implementation ensures the create-team command is now resilient to temporary GitHub API issues while maintaining safety through idempotency checks.

Fixes #1381.

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[github-actions]

Unit Test Results

  1 files    1 suites   20s ⏱️
901 tests 901 ✅ 0 💤 0 ❌
902 runs  902 ✅ 0 💤 0 ❌

Results for commit 9524d1c.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Octoshift	87%	76%	1445	✔
bbs2gh	82%	76%	669	✔
gei	81%	73%	596	✔
ado2gh	84%	78%	618	✔
Summary	84% (7288 / 8626)	76% (1712 / 2262)	3328	✔