docs: CLAUDE.md z-index values for barToggleBtn disagree with code and with the doc's own DOM-structure diagram (6 vs 8)

[carochacs]

CLAUDE.md's "Panel object shape" and "Controls bar hide/show system" sections both state barToggleBtn has z-index:6. The DOM-structure diagram later in the same document, and the actual code, disagree:

• screen.js:1311 — .bar background rule includes z-index:7
• screen.js:1323 — barToggleBtn inline style: z-index:8
• screen.js:1010 — viz popover: z-index:9 (comment: "z-index 9 sits above bar (7) and barToggleBtn (8)")

So the actual/documented-elsewhere stack is bar=7 < barToggleBtn=8 < popover=9, matching the doc's intent ("barToggleBtn always on top of the bar"). The two "z-index:6" references for barToggleBtn are stale and, if taken literally, would put the toggle button under the bar — inverting the intended stacking.

Fix: update the two z-index:6 references (Panel object shape section, Controls bar section) to z-index:8 to match code and the DOM-structure diagram.

[pullfrog]

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