`getScopedRecord` returned an existing record without re-inserting it, so the
per-tab record map evicted by insertion order rather than recency. A long-lived
active tab is the oldest key, so crossing the 32-scope cap silently dropped its
tracked model and reset the pill to "Model". Desktop's scope cache does
delete-then-set for exactly this reason.
Also moves the shared session-option tests to src/shared so the root suite runs
them (they only exercised src/shared logic the Electron renderer consumes, but
sat under mobile/ where only mobile's vitest project sees them), and restores
two "why" comments dropped while extracting the shared modules.
Brennan Benson
fb3e18fcdc