Replace Portfolio's static "+ Create new investigation" link (href:
/investigations/case-1) with a <button> that allocates an opaque
application-owned durable ID via crypto.randomUUID() and navigates
via router.push to /investigations/{id} without persisting any empty
Investigation.
INVESTIGATION_ID constant retained only for card links (Continue
investigation / View report) — not migrated in this increment.
Test: deterministic Create New activation test verifies UUID allocation,
navigation to generated ID route, and zero saveInvestigation calls.
robbond
4b55ad1eae