fix(artifacts): sync the decision store, which no allowlist glob matched

gstack-decision-log enqueues projects/<slug>/decisions.jsonl after every write,
but none of the 16 managed globs matched it, so compute_paths_to_stage rejected
every one at its "must match at least one allowlist glob" check.

The writer and the syncer disagreed silently: enabling artifacts sync backed up
learnings, plans, designs and timelines -- everything except the durable decision
ledger -- and nothing reported a miss, because a dropped path prints exactly what
a synced one does when the queue is otherwise empty.

Add the three decisions.* globs and class them artifact so they also sync in
artifacts-only mode.

The test reads the heredocs out of the script rather than executing it:
gstack-artifacts-init.test.ts drives the real script through #!/bin/bash shims and
a colon-separated PATH, so it cannot run on Windows -- the platform where the
companion slug bug bit.

bin/gstack-artifacts-init

@@ -291,6 +291,14 @@ projects/*/*-design-*.md
 projects/*/*-test-plan-*.md
 projects/*/*-eng-review-test-plan-*.md
 projects/*/timeline.jsonl
+# The decision store. gstack-decision-log enqueues projects/<slug>/decisions.jsonl
+# after EVERY write, but no glob above matched it, so compute_paths_to_stage rejected
+# all of them at its "must match at least one allowlist glob" check -- a writer
+# enqueueing a path the syncer is guaranteed to drop. Without these the durable
+# decision ledger never leaves the machine, on any platform.
+projects/*/decisions.jsonl
+projects/*/decisions.active.json
+projects/*/decisions.archive.jsonl
 retros/*.md
 developer-profile.json
 builder-journey.md
@@ -318,6 +326,9 @@ cat > "$GSTACK_HOME/.brain-privacy-map.json" <<'EOF'
   {"pattern": "projects/*/*-design-*.md", "class": "artifact"},
   {"pattern": "projects/*/*-test-plan-*.md", "class": "artifact"},
   {"pattern": "projects/*/*-eng-review-test-plan-*.md", "class": "artifact"},
+  {"pattern": "projects/*/decisions.jsonl", "class": "artifact"},
+  {"pattern": "projects/*/decisions.active.json", "class": "artifact"},
+  {"pattern": "projects/*/decisions.archive.jsonl", "class": "artifact"},
   {"pattern": "retros/*.md", "class": "artifact"},
   {"pattern": "builder-journey.md", "class": "artifact"},
   {"pattern": "projects/*/timeline.jsonl", "class": "behavioral"},

test/artifacts-allowlist-decisions.test.ts

@@ -0,0 +1,66 @@
+import { describe, test, expect } from "bun:test";
+import * as fs from "fs";
+import * as path from "path";
+
+const ROOT = path.resolve(import.meta.dir, "..");
+const INIT = fs.readFileSync(path.join(ROOT, "bin", "gstack-artifacts-init"), "utf-8");
+
+/** Pull a quoted heredoc body out of gstack-artifacts-init by target filename. */
+function heredoc(target: string): string {
+  const re = new RegExp(`cat > "\\$GSTACK_HOME/${target}" <<'EOF'\\n([\\s\\S]*?)\\nEOF\\n`);
+  const m = INIT.match(re);
+  if (!m) throw new Error(`heredoc for ${target} not found in gstack-artifacts-init`);
+  return m[1];
+}
+
+/** fnmatch.fnmatchcase semantics, as compute_paths_to_stage applies them:
+ *  `*` does not cross a path separator. */
+function globToRe(g: string): RegExp {
+  return new RegExp("^" + g.split("*").map((s) => s.replace(/[.]/g, "[.]")).join("[^/]*") + "$");
+}
+
+const DECISION_PATHS = [
+  "projects/acme-widget/decisions.jsonl",
+  "projects/acme-widget/decisions.active.json",
+  "projects/acme-widget/decisions.archive.jsonl",
+];
+
+/**
+ * gstack-decision-log:40 enqueues projects/<slug>/decisions.jsonl after EVERY write,
+ * but no managed glob matched it, so compute_paths_to_stage rejected all of them at
+ * its "must match at least one allowlist glob" check. The writer and the syncer
+ * disagreed silently: turning artifacts sync on backed up learnings, plans, designs
+ * and timelines -- everything EXCEPT the durable decision ledger -- and nothing
+ * anywhere reported a miss, because a dropped path prints exactly what a synced one
+ * does when the queue is otherwise empty.
+ *
+ * Source-level rather than end-to-end: gstack-artifacts-init.test.ts drives the real
+ * script through #!/bin/bash shims and a colon-separated PATH, so it cannot run on
+ * Windows -- which is the platform where this bug bit.
+ */
+describe("the artifacts allowlist covers the decision store", () => {
+  const globs = heredoc("\\.brain-allowlist")
+    .split("\n")
+    .map((l) => l.trim())
+    .filter((l) => l && !l.startsWith("#"));
+
+  test("every decisions.* path matches at least one allowlist glob", () => {
+    for (const p of DECISION_PATHS) {
+      expect({ p, matched: globs.some((g) => globToRe(g).test(p)) }).toEqual({ p, matched: true });
+    }
+  });
+
+  test("decisions.* are class artifact, so they sync in artifacts-only mode too", () => {
+    const map = JSON.parse(heredoc("\\.brain-privacy-map\\.json"));
+    for (const p of DECISION_PATHS) {
+      const hit = map.find((e: { pattern: string; class: string }) => globToRe(e.pattern).test(p));
+      expect({ p, cls: hit?.class }).toEqual({ p, cls: "artifact" });
+    }
+  });
+
+  test("the allowlist still ends with the user-additions marker", () => {
+    // Additions below it survive re-init; a glob added above would be silently
+    // overwritten the next time gstack-artifacts-init runs.
+    expect(heredoc("\\.brain-allowlist").trimEnd()).toMatch(/# ---- USER ADDITIONS BELOW ----/);
+  });
+});