…rows

Clarify test comment: the second test confirms followLatestIfPinned
snaps scroll to bottom when fired. The structural guarantee (pinned-todo
element is observed) is separately asserted in test 1, which is the
check that goes red on main without the fix.

…nnedTodoSlot mount detection

The MutationObserver was only watching the .chat-log element. PinnedTodoSlot
(.chat-pinned-todo) is a sibling of .chat-log-wrap inside .pane, outside the
observed subtree. syncPinnedTodo inside the MutationObserver callback was
therefore dead code for mount/unmount transitions of the slot.

Add a second observation on paneEl (el.parentElement?.parentElement) with
childList-only so the MutationObserver fires when PinnedTodoSlot mounts or
unmounts and syncPinnedTodo can register/deregister the element with the
ResizeObserver.

Add Playwright spec that goes red on origin/main and green on this fix
branch. Scenario A asserts that a chat-log pinned to the bottom snaps
back after the PinnedTodoCard grows (the ResizeObserver-on-pinned-todo
path). Scenario B asserts that a deliberate scroll-up is not overridden.

Also allow OD_WORKSPACE_ROOT env override in next.config.ts so Turbopack
resolves node_modules correctly when the web app is booted from a worktree
whose node_modules symlinks resolve outside the default workspace root.

PinnedTodoSlot sits outside the .chat-log scroll container, so the
ResizeObserver and MutationObserver coverage that keeps auto-scroll
working when the todo card grows is non-obvious to future implementers.
Document the invariant in the Chat UI conventions section.

…tion

…ndition unconditional

…back

… test branch

Three follow-ups to nettee's review feedback:

1. apps/web/next.config.ts gains a pnpm-workspace.yaml existence check
   after the relative-path validation. Without it, an override like
   '<repo>/apps' or '<repo>/apps/web' passes the relative(resolved, WEB_ROOT)
   check but the resolved path is missing the sibling packages/* directory
   that apps/web imports from (for example @open-design/contracts). Next
   would later fail deep inside file tracing / Turbopack with a much
   harder-to-diagnose error. Now we throw at config load with a clear message.

2. e2e/ui/chat-todo-autoscroll.test.ts drops the redundant
   'if (scrollUpOccurred)' branch. The hard precondition above it already
   guarantees distanceAfterScroll > 80, so the if was dead code that read
   as a false-green path. The body now runs unconditionally.

3. Same test tightens the post-grow assertion. The previous
   toBeGreaterThan(60) would pass even if a regression dragged the log
   most of the way back to the bottom (e.g. before=150, after=61).
   Replaced with Math.abs(distanceAfterGrow - distanceAfterScroll) less than
   SCROLL_PRESERVATION_TOLERANCE_PX (20) — a delta check that actually
   verifies the comment's claim of 'within ~20px of where the user left it'.

…cenario B assertion

- Use realpathSync on both resolved and WEB_ROOT before the ancestor check so
  that symlinked paths (macOS /tmp vs /private/tmp, worktree checkouts) compare
  correctly instead of false-throwing on a physically valid override.
- Add isAbsolute(rel) guard for the Windows cross-drive case where path.relative()
  returns an absolute path instead of a ..-prefixed string.
- Scenario B: replace distance-to-bottom delta assertion with scrollTop preservation
  check. Growing the pinned todo naturally increases distance-to-bottom by ~extraPx
  (clientHeight shrinks while scrollTop is held fixed), so the old Math.abs(after -
  before) < 20 check would fail on correct behavior. asserting scrollTop directly
  catches the real regression: followLatestIfPinned incorrectly snapping a non-pinned
  user back to the bottom.
- Add hard precondition that clientHeight actually changed so the test fails fast
  if the layout stops exercising the non-pinned path.

…unit test