Evaluate expressions before executing activities - #483

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Codex PR Review

Medium: activity-state expressions can be evaluated too early

ExpressionReferencesActivityState only preserves direct $data.activity access where activity is the first suffix on $data. Equivalent jq forms such as ${ $data | .activity.attempt } or ${ $data as $d | $d.activity.attempt } are not detected, so ResolveActivityInput evaluates them workflow-side before AddActivityInfo exists. That turns the value into null instead of preserving it for activity-side evaluation. This is a correctness regression for HTTP with payloads that previously evaluated inside the activity.
activity_expressions.go, runtime_expressions.go

Concrete fix: broaden the preservation analysis to cover jq data-flow forms that derive from $data, or fail closed for any expression where $data is piped or aliased before an activity lookup. Add regression tests for pipeline and alias forms.

I could not run tests because the sandbox is read-only and Go could not create its module cache.