fix(workflow): detect nested git worktree in new-project bootstrap (#3491)

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>

tests/prompt-injection-scan.test.cjs

@@ -52,6 +52,7 @@ const SCAN_EXTS = new Set(['.md', '.cjs', '.js', '.json']);
 const ALLOWLIST = new Set([
   'get-shit-done/bin/lib/security.cjs',        // The security module itself
   'get-shit-done/workflows/discuss-phase.md',  // Large workflow (~50K) with power mode + i18n
+  'get-shit-done/workflows/new-project.md',     // Large workflow (~50K) — agent install, runtime detect, brownfield map, #3491 worktree gating
   'get-shit-done/workflows/execute-phase.md',  // Large orchestration workflow (~51K) with wave execution + code-review gate
   'get-shit-done/workflows/plan-phase.md',      // Large orchestration workflow (~51K) with TDD mode integration
   'hooks/gsd-prompt-guard.js',                  // The prompt guard hook