feat(ui): for_each entries drawn inset in the flow view

[dkackman]

A list-driven step (for_each) showed as one box on the job page's flow view while its members ran one by one in the Progress list. The group box now grows and renders one inset chip per entry:

• chips named as the workflow wrote them (entry name, else index - _entry_keys's rule), with the engine's group@entry name on hover
• a chip greens as its step_end arrives; the running one pulses amber
• the group box keeps its existing rule (amber while any member runs, green only when all are done); arrows and fan-in labels still attach to the group box
• members are read from the definition - a literal for_each list, or a variable: resolved against variables, which the realized workflow carries with the run's actual list folded in (dw/realize.py) - so historical jobs show their members too, with no server change; a list that cannot be read statically shows a muted for_each stand-in
• column layout is height-aware so a tall box no longer overlaps the node beneath it

One bug the TDD loop caught on the way: between one entry finishing and the next starting, activeMember still reported the just-ended member and its chip stayed amber - it now reports nothing in that gap.

Test evidence

• vitest 214/214 (36 new across flow/runstate/FlowView/JobPage)
• svelte-check 0 errors, eslint clean, npm run build exit 0
• throwaway e2e against a real server and a fast-failing for_each job: job page screenshotted with the chips rendering, then the spec deleted

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