fix(elements): keep chain-of-thought timeline connector continuous between steps

[ephraimduncan]

Problem

The vertical timeline connector in ChainOfThoughtStep has three visual defects, visible on the chain-of-thought docs/example page:

1. Disappears on short steps — the connector is positioned top-7 (28px) inside an icon column that is only ~18px tall for a label-only step, so its height clamps to zero and nothing is painted.
2. Breaks between steps — it ends at bottom-0 of its own step box, so it can't bridge the 12px space-y-3 gap that ChainOfThoughtContent adds between steps.
3. Dangling stub after the last step — the connector renders unconditionally with no awareness of being the final item.

Fix

• Start the connector at top-6 (8px below the icon) and extend it with -bottom-3 so it spans the inter-step gap exactly.
• Mark the step root as a named group (group/step) and hide the connector on the last step via group-last/step:hidden.

Verification

Measured on the rendered docs page (/components/chain-of-thought): each connector's bottom edge now lands exactly on the next step's top (no gap, no zero-height segment), and the final step's connector is display: none. Zoomed screenshot inspection confirms a continuous rule between every adjacent icon pair and no line after the final icon.

Before / after connector on a label-only step: previously unpainted (used height clamped to 0); now an 8px visible segment bridging into the next step.

Screenshots

Before — annotated

After — annotated

[vercel]

@ephraimduncan is attempting to deploy a commit to the Vercel Team on Vercel.

A member of the Team first needs to authorize it.