create-handoff

# Create Handoff Write a session handoff file at `.turbo/handoff/<YYYY-MM-DD>-<slug>.md` so a fresh session can pick up where this one left off. ## Step 1: Resolve the Target Path Get today's date: `date +%Y-%m-%d`. Pick a slug for the current task: - Lowercase - Replace non-alphanumeric characters with hyphens - Collapse consecutive hyphens - Trim leading and trailing hyphens - Truncate to 40 characters at a word boundary If the work is anchored to an existing plan at `.turbo/plans/<slug>.md`, reuse that plan's slug verbatim. The user may pass an explicit slug or output path; honor it. Resolve the repo root with `git rev-parse --show-toplevel`, except inside a linked worktree — where `git rev-parse --git-dir` differs from `--git-common-dir` — in which case use the parent of the common dir, so the handoff lands in the main checkout rather than in a worktree that is destroyed with its branch. The target path is `.turbo/handoff/<YYYY-MM-DD>-<slug>.md` under that root. A generated slug takes `-2`, `-3`, and so on until the path is free. When the user supplied the slug or path and it already exists, use `AskUserQuestion` to offer overwrite, a numeric suffix, or a different slug. When an open decision will outlive the rest of the session's state, still unresolved while the work around it is finished, give it its own handoff. Everything else stays in a single file. Slug the split handoff for that decision rather than appending a collision suffix, and write it to stand alo...