fix: CU-2377 scip-go is logging errors that should be classified as warnings

[chrapkowski-sg]

Changes log.Error to log.Warn for two conditions in the package loader that are recoverable edge cases with explicit fallbacks, not actual errors:

• Unknown version for userland package - When a package lacks an explicit version and isn't the main module, we set a fallback version "." and continue normally.
• Unable to extract revision from pseudo-version - When parsing a pseudo-version fails, we use the original version and continue.

Both conditions have graceful fallbacks and don't indicate failures. Logging them as ERROR was misleading and noisy in production logs.

I removed ErrOrPanic call since we do not do this in other places where we log a warn for example

scip-go/internal/loader/loader.go

Line 111 in 05ce6e6

log.Warn("No target patterns provided using default './...'")

[chrapkowski-sg]

This change is part of the following stack:

• fix: CU-2377 scip-go is logging errors that should be classified as warnings #178 ◀

_{Change managed by git-spice.}

[peterguy]

Based on the Slack discussion this is probably not the correct solution. The actual fix is probably handling multi-module repos in normalizePackage, not silencing the log.