Merge 3e9b009642 without changing shutdown scheduling or recovery behavior. Migrate regression fixtures to opaque LayerNode replacements and retain fresh Instance selection around each stub runner, including the upstream helper compile fix.
Replace exposed layer graph assembly with opaque declarations, checked substitutions, and lifetime-aware compilation. Preserve deep replacement, ordered startup, and Effect-owned resource lifetimes; migrate callers and verify source and published package contracts.
Keep the title and workspace label above scrollable sidebar details. Disable the unused horizontal scrollbar and place the automatic vertical scrollbar in the reserved gutter so tab changes do not flash or shift the sidebar.
Keep the startup yield and started hook in one uninterruptible region. A successor selected during cleanup must write its recovery claim before shutdown can terminalize it; the runner remains interruptible.
Count executed startup effects in scheduler tests and cover shutdown from a joined caller with real execution claims and restart recovery.
Keep the open-coordinator decision and settlement in one synchronous callback. Separating them with an Effect boundary permits shutdown to skip both successor start and suspension.
Sweep scheduler-yield boundaries in the retiring execution and document why settlement cannot be lifted into unconditional ensuring.
Evaluate the suspension callback inside its cleanup guarantee so synchronous throws cannot leave ghost ownership. Cover successful hooks, returned defects, and synchronous throws.
Stop scheduling before the execution FiberSet closes. Preserve a pending successor claim after the previous terminal settles, without forking into a closed set or leaving ghost ownership.
Cover user-interruption cleanup, terminal settlement, sequential and parallel scope closure, and restart recovery of an admitted move.
Configure custom Markdown renderers before assigning content and share a reactive message-position index across assistant footers. Preserve completion ordering and historical footer metrics, with regression coverage for prepend, same-length refresh, and revert.
