fix(#2623): resolve parent .planning root for sub_repos workspaces in SDK query dispatch (#2629)

* fix(#2623): resolve parent .planning root for sub_repos workspaces in SDK query dispatch

When `gsd-sdk query` is invoked from inside a `sub_repos`-listed child repo,
`projectDir` defaulted to `process.cwd()` which pointed at the child repo,
not the parent workspace that owns `.planning/`. Handlers then directly
checked `${projectDir}/.planning` and reported `project_exists: false`.

The legacy `gsd-tools.cjs` CLI does not have this gap — it calls
`findProjectRoot(cwd)` from `bin/lib/core.cjs`, which walks up from the
starting directory checking each ancestor's `.planning/config.json` for a
`sub_repos` entry that lists the starting directory's top-level segment.

This change ports that walk-up as a new `findProjectRoot` helper in
`sdk/src/query/helpers.ts` and applies it once in `cli.ts:main()` before
dispatching `query`, `run`, `init`, or `auto`. Resolution is idempotent:
if `projectDir` already owns `.planning/` (including an explicit
`--project-dir` pointing at the workspace root), the helper returns it
unchanged. The walk is capped at 10 parent levels and never crosses
`$HOME`. All filesystem errors are swallowed.

Regression coverage:
- `helpers.test.ts` — 8 unit tests covering own-`.planning` guard (#1362),
  sub_repos match, nested-path match, `planning.sub_repos` shape,
  heuristic fallback, unparseable config, legacy `multiRepo: true`.
- `sub-repos-root.integration.test.ts` — end-to-end baseline (reproduces
  the bug without the walk-up) and fixed behavior (walk-up + dispatch of
  `init.new-milestone` reports `project_exists: true` with the parent
  workspace as `project_root`).

sdk vitest: 1511 pass / 24 fail (all 24 failures pre-existing on main,
baseline is 26 failing — `comm -23` against baseline produces zero new
failures). CJS: 5410 pass / 0 fail.

Closes #2623

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(#2623): remove stray .planing typo from integration test setup

Address CodeRabbit nitpick: the mkdir('.planing') call on line 23 was
dead code from a typo, with errors silently swallowed via .catch(() => {}).
The test already creates '.planning' correctly on the next line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/CONFIGURATION.md

@@ -227,6 +227,17 @@ All workflow toggles follow the **absent = enabled** pattern. If a key is missin
 | `planning.search_gitignored` | boolean | `false` | Add `--no-ignore` to broad searches to include `.planning/` |
 | `planning.sub_repos` | array of strings | `[]` | Paths of nested sub-repos relative to the project root. When set, GSD-aware tooling scopes phase-lookup, path-resolution, and commit operations per sub-repo instead of treating the outer repo as a monorepo |
 
+### Project-Root Resolution in Multi-Repo Workspaces
+
+When `sub_repos` is set and `gsd-tools.cjs` or `gsd-sdk query` is invoked from inside a listed child repo, both CLIs walk up to the parent workspace that owns `.planning/` before dispatching handlers. Resolution order (checked at each ancestor up to 10 levels, never above `$HOME`):
+
+1. If the starting directory already has its own `.planning/`, it is the project root (no walk-up).
+2. Parent has `.planning/config.json` listing the starting directory's top-level segment in `sub_repos` (or the legacy `planning.sub_repos` shape).
+3. Parent has `.planning/config.json` with legacy `multiRepo: true` and the starting directory is inside a git repo.
+4. Parent has `.planning/` and an ancestor up to the candidate parent contains `.git` (heuristic fallback).
+
+If none match, the starting directory is returned unchanged. Explicit `--project-dir /path/to/workspace` is idempotent under this resolution.
+
 ### Auto-Detection
 
 If `.planning/` is in `.gitignore`, `commit_docs` is automatically `false` regardless of config.json. This prevents git errors.