Follow-up to the salvaged worktree-materialization fix. When a worktree
task has no explicit workspace_path, resolve the anchor from the board's
default_workdir (a git repo) and materialize <repo>/.worktrees/<id> per
task, instead of silently rooting under the dispatcher's CWD (whatever
directory launched the gateway, e.g. the Hermes checkout). If no
default_workdir is configured, raise with a clear message rather than
guessing from CWD.
Adds AUTHOR_MAP entry for the salvaged commit.
15cfc2836f