docs(virtual): link the remote exclusion reasons in the Reason docs

What

Two Reason value docs in internal/virtual/rules.go named a cross-package identifier as plain text while every other one in the file is written as a godoc doc link:

• ReasonInvalidRule named remote.ExclusionInvalidRule (line 184 on main)
• ReasonUnexpectedKind named remote.ExclusionUnexpectedKind (line 196 on main)

Both are now bracketed, so the two adjacent const docs render the same way instead of one form each. The package imports internal/remote, so the links resolve; [remote.ErrNoUpstreams], [remote.ErrAllUpstreamsDenied], and [remote.ErrAllUpstreamsIneligible] in the same file already use this form.

The ReasonUnexpectedKind doc also carried a mid-sentence line break after "data error". Reflowed in the same edit.

No code changes. 6 lines changed, all comments.

Why

This MR originally rewrote four doc comments to state that a ReasonInvalidRule upstream is recorded in the exclusion audit stream, not only error-logged. That correction landed on main independently in e75e56448 ("feat(virtual): scope rules, split aggregates, fail unexpected kinds"), which rewrote all four comments and says more than this branch did, because the same commit added a third Reason value. main also corrects the two sibling sites that carried the same stale claim: the loadAndFilter doc in resolve.go and the TestEligibleUpstreams doc in rules_test.go.

The branch has been rebased onto main, discarding the branch side of all four blocks. What remains is the doc-link change, which main does not have. It came from the two Duo review threads on this MR, extended to the sibling constant on the reviewer's non-blocking note.

resolve.go and upstream.go name these same constants as plain text too, but those files use plain text for cross-package identifiers almost everywhere, so bracketing them is a separate consistency pass rather than this MR's scope.

Test plan

Comment-only change. go build ./internal/virtual/, go vet ./internal/virtual/, and golangci-lint run ./internal/virtual/ (0 issues) pass locally; go test and golangci-lint ran in the pre-commit hook. go doc -all ./internal/virtual renders both identifiers in bracketed form.

No e2e scenario is added or affected: the change is documentation-only and alters no request path.