test(lcms): disperse PR #232 review tests (B1–B7) into per-subject suites

[PiTrem]

Stacked on #313 (base = fix/cv-density-submit-factor). Will retarget to 231-display-lcms-data once #313 merges. Tests only — no behaviour change.

What

The B1–B7 review regression tests were carried in a single PR-named file, src/__tests__/units/pr232_review_blocking.test.tsx, which served its purpose as the red→green proof for #232's blockers. As a permanent fixture it fought the repo's subject-based test layout. This PR moves each test into the suite that owns the code it guards and deletes the combined file.

Finding	Now lives in
B1 — peak-add on a non-LCMS layout dispatches EDITPEAK.ADD_POSITIVE	sagas/saga_ui_lcms.test.tsx (alongside the existing PEAK_ADD LCMS cases)
B2 — getArea on cumulative-k (NMR/CV) data	helpers/integration.test.tsx
B3 — getAbsoluteArea from raw y	helpers/integration.test.tsx
B4 — Convert2Peak honours stored LC/MS peaks + offset	helpers/chem.test.tsx
B7 — convertThresEndPts empty-on-cleared precondition	helpers/chem.test.tsx
B5 — CV current-density chart factor	components/d3_multi/multi_focus.test.js (new)
B7 — drawBar empty-endpoint guard	components/d3_line_rect.test.js

Two deliberate changes from a straight move

• B6 dropped, not moved. Its test only re-implemented the source access forms inline (ViewerLineRect isn't exported), so it exercised no real component code — a tautology that gives false confidence in a permanent suite. Removed and tracked as a follow-up: it needs a testable seam (export ViewerLineRect, or extract the uvvis-seed builder) before it can guard the real componentDidUpdate guard.
• B5 submit/export factor not duplicated. computeCvYScaleFactor is already covered in components/cmd_bar/r05_submit_btn.test.js (added in fix(cv): apply CV current-density factor once on submit/export (B5 remainder, for #232) #313). The B5 test moved here covers the chart factor (multi_focus.computeYTransformFactor), the other call site.

Test

All moved assertions stay green on the branch head:

helpers/integration.test.tsx · sagas/saga_ui_lcms.test.tsx · helpers/chem.test.tsx
components/d3_multi/multi_focus.test.js · components/d3_line_rect.test.js
→ Test Suites: 5 passed, Tests: 91 passed

refs #232