ArtifactFS 1.0.0-rc.5

Release candidate patch for ArtifactFS 1.0.

This supersedes 1.0.0-rc.4 and hardens repository preparation against transient upstream Git failures.

Changes since 1.0.0-rc.4:

• Retry transient blobless clone and prepared-repository fetch failures with bounded jitter and fresh clone directories.
• Recognize common Git, cURL, HTTP, Cloudflare timeout, disconnect, truncated response, and pack transport failures while avoiding retries for authentication, rate-limit, and local storage errors.
• Preserve both the transport failure and caller cancellation when a deadline interrupts Git.
• Terminate Git transport descendants on cancellation without converting a successfully completed command into a deadline failure.
• Scope inline HTTP credentials to the original remote authority, reject malformed credential URLs, and redact reflected credentials from errors and logs.

Verification:

• PR #29 Build & Test, CodeQL, and Semgrep checks passed.
• Local release validation: go build ./cmd/artifact-fs, go vet ./..., go test ./..., and go test -race ./internal/gitstore.
• Linux and Windows gitstore test binaries cross-compiled successfully.