Implement Option B (enhanced env var) for T058.S2:
- Support multiple S3 credentials via S3_CREDENTIALS env var
- Format: "key1:secret1,key2:secret2,..."
- Backward compatible with S3_ACCESS_KEY_ID/S3_SECRET_KEY
- Add tests for both multi and single credential formats
This unblocks T039 production deployment while proper IAM
credential service (T060) is implemented separately.
Tests: 10/10 auth tests pass (added 2 new credential tests)
Refs: T058.S2 Option B (approved), T060 (proper IAM integration)
- Remove gitlinks (160000 mode) for chainfire, flaredb, iam
- Add workspace contents as regular tracked files
- Update flake.nix to use simple paths instead of builtins.fetchGit
This resolves the nix build failure where submodule directories
appeared empty in the nix store.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
