Update go-gather dependency to v1.1.0

[robnester-rh]

Summary

Once conforma/go-gather v1.1.0 is released, update the dependency in conforma/cli and verify compatibility with the behavioral changes.

Blocked by

• conforma/go-gather v1.1.0 release (see tracking issue)

Required changes

go.mod bump

go get -u github.com/conforma/go-gather@v1.1.0

Verification checklist

• make test passes with new go-gather version
• make acceptance passes (if applicable)
• Verify logMetadata debug output fires for all gatherer types (OCI, Git, file) — go-gather #299 fixes the pointer/value mismatch that caused silent assertion failures
• Verify bitbucket.org URLs route to Git gatherer correctly — go-gather #300 fixes the HTTP/Git routing
• Verify OCI pulls work with new user-agent ("go-gather" instead of "conftest")
• Verify localhost OCI registry still works — go-gather #300 fixes overly broad localhost replacement
• Search test assertions for hardcoded go-gather error message strings that may have changed due to added error wrapping context

No code changes expected

The go-gather changes are designed to be backward-compatible. The metadata pointer fix (#299) makes the cli's existing pointer type assertions in internal/policy/source/source.go (logMetadata function) work correctly without any cli-side changes.

Consumer-facing behavioral changes to note in release

• OCI registry User-Agent changed from "conftest" to "go-gather" — if any OCI registries or proxies filter on this header, they may need updating
• bitbucket.org URLs now route to Git gatherer instead of HTTP