fix(chat): pin streaming responses to the composer; open remote-only branches as worktrees

[enisze]

Two independent fixes reported from the same session.

Streaming responses sat far above the composer

Sending made the new user message a LegendList anchoredEndSpace target, which reserved a viewport-tall blank tail below it and switched maintainScrollAtEnd off. Until a turn outgrew that reserve, the response stayed pinned near the top of the timeline with a large gap between the text and the composer.

The anchored tail is gone: the timeline always maintains scroll at the end, so a streaming turn hugs the composer. That removes the anchor plumbing whose only job was positioning and re-settling that reserve (~200 lines in ChatView), and replaces timelineScrollAnchoring with timelineScroll — keeping the overflow probe the follow effect already needed. Scroll-away behaviour is unchanged: a wheel/touch/pointer gesture still parks the view and shows the "Scroll to end" pill.

Selecting a remote-only branch created no worktree

listRefs reports a remote ref as { name: "origin/claude/x", remoteName: "origin" } — the prefix is already in name. The workspace picker's branch suggestions concatenated both fields, and the pull-request dialog matched candidate refs against that same doubled shape. Picking a branch that exists only on origin sent origin/origin/claude/x, matched nothing, and silently produced no worktree. That is the normal case for an agent-pushed claude/* branch; a branch already present locally worked, which made it look intermittent.

Suggestions now pass and display the ref name as listed, and a reference resolves through findBranchRefForReference, which accepts either the qualified origin/claude/x or the plain claude/x and prefers a local ref over a remote one. The new shared stripRemoteRefPrefix strips only a ref's own remote prefix, so a local claude/x keeps every segment; baseRefChoices drops its private copy of that logic.

Picking such a branch now runs git worktree add -b claude/x <path> origin/claude/x, roots the chat in that worktree, and the diff resolves its base via upstream → provider default, so it shows the branch's changes. The base-branch selector on the right is untouched.

Verification

• Workspace typecheck: clean apart from pre-existing failures (DesktopClientSettings.test.ts fixture from 3396b19, effect-lint noise in WorkspaceSearchIndex.test.ts).
• oxlint clean on the touched files.
• Full web unit project green (193 files / 1786 tests); one unrelated flake, stashImageCompression.test.ts timing out under parallel load, passes on its own.
• New tests: timelineScroll.test.ts, stripRemoteRefPrefix, findBranchRefForReference, plus a rewritten MessagesTimeline case asserting no reserved tail.

Not covered: a manually typed origin/claude/x while a local claude/x exists still dead-ends, because the server-side ref search filters by substring on the full string. Clicking a suggestion is unaffected.

🤖 Generated with Claude Code