fix(gbrain-sync): sourceLocalPath handles wrapped {sources:[...]} shape from gbrain v0.30+

[Evode-Manirahari]

Problem

After upgrading to gstack v1.40.0.0 + gbrain v0.30.0.0 or newer (current released gbrain is v0.37.1.0), the first /sync-gbrain after upgrade dies before any stage runs:

$ /sync-gbrain
[gbrain-sync] mode=incremental engine=pglite
gstack-gbrain-sync fatal: list.find is not a function.
(In 'list.find((s) => s.id === sourceId)', 'list.find' is undefined)

Root cause

gbrain sources list --json started wrapping its output as {"sources":[...]} in gbrain v0.30+. The v1.40 hostname-fold migration helper sourceLocalPath() (added in #1547, bin/gstack-gbrain-sync.ts:291) typed the response as a bare array and called .find() on it directly:

// before
const list = execGbrainJson<Array<{ id: string; local_path?: string }>>(...);
if (!list) return null;
const found = list.find((s) => s.id === sourceId);  // crash: list is an object, not an array

The sibling helper in lib/gbrain-sources.ts (statusForSourceId, lines 72-85) already unwraps both shapes correctly — sourceLocalPath was the lone holdout because it was added separately in the v1.40 migration work.

Actual output on a current gbrain:

$ gbrain sources list --json
{
  "sources": [
    { "id": "default", "name": "default", ... },
    { "id": "gstack-code-myrepo-b6de5213", "local_path": "/Users/me/myrepo", ... }
  ]
}

Fix

Accept both wire shapes (defense against the same regression in either direction):

const raw = execGbrainJson<
  | Array<{ id: string; local_path?: string }>
  | { sources?: Array<{ id: string; local_path?: string }> }
>(["sources", "list", "--json"], { baseEnv: env });
if (!raw) return null;
const list = Array.isArray(raw) ? raw : raw.sources || [];
const found = list.find((s) => s.id === sourceId);

Tests

Three new cases in the existing sourceLocalPath describe block in test/gstack-gbrain-sync.test.ts:

1. returns local_path when gbrain wraps the list as {sources: [...]} (v0.30+ shape) — the regression.
2. returns null when the wrapped {sources: [...]} shape has no matching id.
3. treats {sources: undefined} the same as an empty list — defensive case for partial responses.

The existing 3 bare-array tests still pass, locking in backward compat with pre-v0.30 gbrain shims.

Run: bun test test/gstack-gbrain-sync.test.ts → 38 pass, 0 fail (130 expect() calls).

Repro on a fresh machine

# Upgrade gstack to v1.40 (in CHANGELOG, v1.40.0.0 — the hostname-fold migration release)
# Have a working gbrain >= v0.30
cd <any-git-repo>
/sync-gbrain
# → "gstack-gbrain-sync fatal: list.find is not a function"

Found via

Hit this while syncing a freshly-shipped repo against gbrain v0.37.1.0 from a fresh gstack v1.40.0.0 install. Patched locally first; this PR brings the fix upstream.