The `has_git` boolean returned by `init new-project` and `init ingest-docs`
was derived from a shallow `pathExists(cwd, '.git')` check, so a subdirectory
of an existing repo reported `has_git: false`. The workflow then ran
`git init`, creating a nested `.git` inside the outer worktree and silently
diverting subsequent `gsd-sdk commit` calls into the nested repo.
Replace the shallow check with `git rev-parse --is-inside-work-tree`
semantics in both CJS (`get-shit-done/bin/lib/init.cjs`) and TS
(`sdk/src/query/init.ts`, `sdk/src/query/init-complex.ts`) handlers via a new
shared `gitWorktreeInfoInternal` helper, and expose `git_worktree_root` +
`in_nested_subdir` so the workflows can refuse `git init` inside an existing
worktree and warn that planning files will track to the outer repo.
Regression test: `tests/bug-3491-nested-git-worktree.test.cjs`.
Fixes#3491
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
