Two related issues from the GPT-5.5 food-app run:
1. Bottom navigation rendered without its surface fill, blending into
the cream root background. The strip-redundant-section-fills pass
didn't have any of the navigation roles (`navbar`, `nav`, `tab-bar`,
`bottom-tab-bar`, `top-nav-bar`) in PROTECTED_ROLES, so a navbar
carrying `fill: #FFFFFF` (or any SAFE_LIGHT tint) hit the
"safe-light hedge" branch and got stripped. Real-world navs
intentionally use a white surface to separate from a tinted root —
that fill is intended, not a hedge.
Fix: add the five navigation role names to PROTECTED_ROLES. New
test asserts a `role: navbar` frame with `fill: #FFFFFF` on a
`#FFF8F0` cream root keeps its fill.
2. Empty-src image placeholders inserted by the dispatcher's JSONL
fallback only got auto-filled at the orchestrator's tail (line
~1219, after every subtask completes). On a long brief that's a
visible lag; on an aborted/throwing brief the tail never runs and
images stay placeholder forever.
Fire-and-forget `scanAndFillImages(parentId)` from the dispatcher's
applied path so each subtask's image set starts searching as soon
as it lands. The orchestrator-tail scan still runs and dedups
through `queuedNodeIds`, so this is purely a latency / robustness
improvement (no double fetch).
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