feat(threads): stop grouping same-workspace threads in the sidebar - #445

Upstream is adding manual drag reordering for active threads (pingdotgg/t3code#9729, #9730, #9731, #9750). That conflicts with styal's ordering of active threads by workspace, and styal users would rather drag threads into their own order. This removes the workspace grouping so the drag chain can be taken in as upstream wrote it.

Active threads in the web and desktop sidebar, the mobile Home list, and the tablet sidebar are listed newest first again, as in T3 Code. Threads that share a worktree or an explicitly chosen branch are no longer pulled together, and follow-up threads are no longer indented under the original with a connecting line. New threads still default to an isolated worktree.

The shared workspace sort in client-runtime and its tests are removed. The fork feature ledger entry now covers only the worktree default, and the sidebar guide and the styal differences overview no longer describe grouping.

Before	After

Validation

• Ran the web app against a copy of real data with three active threads: a thread, a code review thread started later on the same worktree, and an unrelated thread in between. Before the change, the review was indented under the original thread with a connector line. After it, the three threads appear newest first with no indentation. The browser console had no errors in either state. Titles from a private project are replaced with made-up ones in the screenshots.
• vp test run for the client-runtime thread sort, web Sidebar.logic, and mobile threadListV2 tests: 172 passed.
• Typecheck of @t3tools/client-runtime, @t3tools/web, and @t3tools/mobile, and the fork feature ledger check, pass.
• Not verified: the mobile Home list and tablet sidebar in a simulator. Their ordering is covered by the mobile list tests, and the removed indentation was the only layout change there.

Written by an agent (Claude Code, claude-opus-5-5).