Issue 16455 runtime reproduction
Baseline: ed9b7ca9c5
Environment: Linux x64, real vp run dev server, Chromium via T3 Browser panel, 1280x800, light theme.

Setup: two independent git repos with one commit each; unrelated has origin https://github.com/octocat/Hello-World.git; app has origin https://github.com/octocat/Spoon-Knife.git. Registered unrelated first, app second through projects.mutate RPC.
No project checks out pingdotgg/t3code.

Browser RPC: pullRequests.detail({projectId:"triage-16455-app",host:"github.com",repository:"pingdotgg/t3code",number:23165})
Result: Success; projectId="triage-16455-unrelated"; workspaceRoot="/tmp/issue-16455-fixture/unrelated"; repository="pingdotgg/t3code".

Real PR panel: opened same reference, selected Check out > In a separate worktree.
Observed: draft title/breadcrumb and hero use unrelated; loading toast Preparing the pull request checkout.
Observed child command: git fetch --quiet --no-tags -- PixPMusic +refs/heads/fix/patched-node-service-updates:refs/remotes/PixPMusic/fix/patched-node-service-updates

First checkout attempt completed with Failed to materialize pull request branch; the PR was merged. A fork remote was nevertheless added to unrelated.

Second attempt: created stopped thread triage-16455-app-thread in app through orchestration.dispatchCommand, linked open GitHub PR 23184 (GitCafe identity 23201), opened that thread, clicked Fix on linked PR row.
Recording 2026-10-22 00:45:59.921 UTC: at ~6s clicked Fix; navigation moves from app / PR handoff reproduction to draft in unrelated; preparation loading toast appears.
Observed command: git fetch --quiet --no-tags -- PixPMusic +refs/heads/pixpmusic/catalog-daybreak:refs/remotes/PixPMusic/pixpmusic/catalog-daybreak