test(runner): pin the owner filter's case-folding at both seams (DEV-2519)

[danielzytohoc]

Hardening follow-up to the DEV-2519 owner filter (task). The feature's suites are green and cover every bullet in the ticket, but audited against docs/TESTING.md ("a test must fail when the control goes away"), two deliberate behaviors had no such test. Both sit on the two-writer created_by casing split (DEV-2501).

Unit — ownerOptions folds two casings into one owner. Every existing fixture is lowercase, so a refactor that keys options on the raw local part (same person listed twice, counts split) passed all 9 tests. Verified by applying exactly that mutation: only the new test catches it.

E2E — a pasted ?owner=SOMEONE.ELSE link. filterByOwner normalises its argument, so dropping the .toLowerCase() from the URL seed in MyDemos.tsx keeps every test green while the grid filters under an "Everyone" label — a lying picker on the exact artefact the ticket calls shareable. The new spec asserts the cards and the label; against that mutation it fails on the label, for the right reason.

Test-only change (+28 lines); both files already run in the CI globs (pipeline/*.test.mjs, unfiltered playwright test). Fresh local runs: unit 10/10, all-demos.spec.ts 12/12.

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Note

Low Risk
Test-only additions; no production behavior or security-sensitive code is changed.

Overview
Adds two tests so the All Demos owner filter cannot silently drop case-folding around mixed created_by casings (browser vs MCP).

A unit test asserts ownerOptions merges two casings of the same address into one option with a combined count. An e2e spec loads ?owner=SOMEONE.ELSE and checks both the filtered cards and that the picker still labels the person, not Everyone.

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