#30831 Deduplicate Cloud Session Info repository rows

Preserves the existing linked folder repository row when a Cloud attachment has the same owner/name, avoiding duplicate repository entries in Session Info while retaining the attachment rows for other repositories.

Validation: bun test webviews/test/session-info-environment.test.tsx -t "attached repository matching" (pass).

Agent session: agent session

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Summary by cubic

Prevents duplicate repository rows in Cloud Session Info when an attached Cloud repo matches the linked folder repository.

Previously, a Cloud attachment with the same owner/name as the folder repository rendered a second row under the section. Attached repos matching the linked folder repository are now filtered out, keeping the original linked row while attachments for other repositories still appear. Test coverage now asserts the retained row stays a GitHub link and unrelated attachments are unaffected.

Validation: bun test webviews/test/session-info-environment.test.tsx -t "an attached repository matching the folder repository keeps one linked row".