test(quality): expand feature validation coverage

[DavidBabinec]

Summary

• Expanded ADMIN-005 shell reliability coverage in the canonical feature matrix and TSV spreadsheet.
• Added ToastProvider regressions for alert/status aria behavior, metadata, and dismiss cleanup through the canonical Toast barrel.
• Exported dismissToast from @ui/components/Toast to match the toast bus API used by producers/tests.
• Added browser regressions for Content workspace panel resize, close/reopen, reload persistence, and 390px mobile containment.
• Capped the rendered left sidebar width on narrow viewports while preserving the stored desktop panel width.
• Capped and mobile-anchored the right sidebar so the Settings close control stays reachable when both sidebars reopen on a phone viewport.

Defects

• DEF-20260623-ADMIN005-01: Toast barrel exported pushToast but not dismissToast, breaking canonical dismiss imports and stale-toast cleanup tests.
• DEF-20260623-ADMIN005-02: Persisted 520px Content left-panel width could push the close affordance beyond a 390px viewport after reload.
• DEF-20260623-ADMIN005-03: Persisted Content + Settings sidebars could place the Settings close affordance at x=684 in a 390px viewport after reload.

Impact

ADMIN-005 now has focused unit coverage plus live browser evidence for workspace shell recovery. Remaining risk is documented for injected route-failure exploratory review.

Verification

• Red focused ADMIN-005 E2E failed on the settings close button at x=684 before the right-sidebar fix.
• Green focused bun run test:e2e -- --project=e2e tests/e2e/admin-navigation.e2e.ts -g "ADMIN-005" passed 2/2 including setup.
• bun run test:e2e -- --project=e2e tests/e2e/admin-navigation.e2e.ts passed 5/5.
• Browser smoke at 390x844 showed both close controls ending at x=384, zero document overflow, no console warnings/errors, and successful Settings close recovery.
• bun run lint passed.
• bun run build passed.
• bun test passed 5703/5703.
• TSV 14-field validation passed for 146 rows.
• git diff --check passed.