docs(workflows): execution semantics, not simultaneity

The concurrency section drifted into 'run at the same time' framing across two
accuracy passes — but the semantics are non-blocking execution: a block starts
the moment its dependencies finish and waits on nothing else. Section retitled
'Blocks run as soon as they can', the rule stated in two plain sentences, the
duplicated pre-image example narration gone (the post-image caption carries it).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ouiliame

apps/docs/content/docs/en/workflows/how-it-runs.mdx

@@ -10,13 +10,13 @@ import { Image } from '@/components/ui/image'
 
 When you run a workflow, Sim works out the order from the [connections](/workflows/connections): a block runs as soon as the blocks it depends on have finished.
 
-## Independent blocks run in parallel
+## Blocks run as soon as they can
 
-A block never waits on a block it isn't downstream of. So when several blocks become ready at the same moment — all their dependencies finished — they run at the same time. Here, both agents are wired straight to Start, so they run side by side; there's nothing to configure.
+A block starts the moment its dependencies finish, and it waits on nothing else.
 
-<Image src="/static/execution/concurrency.png" alt="Two agent blocks running at the same time after the Start trigger" width={800} height={500} />
+<Image src="/static/execution/concurrency.png" alt="Two agent blocks running after the Start trigger" width={800} height={500} />
 
-Here the Customer Support and Deep Researcher agents both run right after the Start trigger, instead of one waiting on the other.
+Here the Customer Support and Deep Researcher agents each depend only on Start, so neither waits for the other.
 
 ## A block waits for all its inputs