fix(gbrain-sources): bump gbrain sources list --json timeout 10s → 30s

Supabase free-tier cold-starts can push `gbrain sources list --json` past
10s (observed 14.5s in the wild), causing probeSource() to throw ETIMEDOUT
during /sync-gbrain code stage even though the underlying CLI was healthy.
Matches the 30s ceiling already used by `sources add` / `sources remove`
in the same file.

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

lib/gbrain-sources.ts

@@ -53,7 +53,7 @@ export function probeSource(id: string, env?: NodeJS.ProcessEnv): SourceState {
   try {
     stdout = execFileSync("gbrain", ["sources", "list", "--json"], {
       encoding: "utf-8",
-      timeout: 10_000,
+      timeout: 30_000,
       stdio: ["ignore", "pipe", "pipe"],
       env,
     });
@@ -164,7 +164,7 @@ export function sourcePageCount(id: string, env?: NodeJS.ProcessEnv): number | n
   try {
     stdout = execFileSync("gbrain", ["sources", "list", "--json"], {
       encoding: "utf-8",
-      timeout: 10_000,
+      timeout: 30_000,
       stdio: ["ignore", "pipe", "pipe"],
       env,
     });