fix(extraresources): preserve namespace when matching by labels

[pujitha24]

Description of your changes

ToResourceSelector converts an ExtraResourcesRequirement into a fnv1.ResourceSelector, but only copied the Namespace field onto the selector inside the matchName branch. Namespace is a top-level field on the proto ResourceSelector, independent of the match oneof (matchLabels vs matchName), so when a requirement combined matchLabels with a namespace, the namespace was silently dropped and the query matched labelled resources across all namespaces instead of the requested one. This reproduces the exact behavior reported in the issue: HTTPRoutes selected by matchLabels with a namespace set came back from every namespace, not just the specified one.

The fix moves the namespace assignment above the matchLabels/matchName branch so it is applied to both selector types instead of only matchName.

Added extraresources_test.go with TestToResourceSelector, covering matchLabels+namespace (the bug scenario), matchLabels without a namespace (cluster-scoped, must remain unset), and matchName+namespace (regression guard for the previously-working path). Ran go test -v -cover ./..., which passed (82.9% coverage); confirmed via git stash that the matchLabels+namespace case fails against the pre-fix code and passes with the fix. Also ran go build ./..., go vet ./..., go mod tidy (no diff), and golangci-lint run ./... at v2.4.0 (the version pinned in this repo's CI workflow), all with no issues. User-visible behavior for matchName selectors is unchanged; the only behavior change is that matchLabels selectors now honor the namespace field as documented, narrowing results to the requested namespace instead of matching cluster-wide.

Fixes #597

I have:

• Read and followed Crossplane's contribution process.
• Added or updated unit tests for my change.

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AI assistance: this change was drafted with Claude Code.

[pujitha24]

Just checking in on this one — it's rebased and all checks are green, happy to make any changes if something would help review go faster.