fix(resolvers): rewrite all gbrain put_page instructions to canonical put <slug>

scripts/resolvers/gbrain.ts emitted user-facing copy-paste instructions
using the renamed `gbrain put_page` subcommand across 10 skills
(office-hours, investigate, plan-ceo-review, retro, plan-eng-review,
ship, cso, design-consultation, fallback, entity-stub). Every gstack
user copying those snippets hit "unknown command: put_page" on gbrain
v0.18+.

This commit:
- Rewrites all 10 instruction templates to use `gbrain put <slug>
  --content "$(cat <<EOF...EOF)"` with title/tags moved into YAML
  frontmatter inside --content, matching the v0.18+ subcommand shape
- Updates README.md and USING_GBRAIN_WITH_GSTACK.md "common commands"
  table to reference `gbrain put` and `gbrain get`
- Adds test/resolvers-gbrain-put-rewrite.test.ts pinning two
  invariants: (a) resolver source ships only canonical instructions,
  (b) every tracked SKILL.md file is free of `gbrain put_page`

CHANGELOG entries are deliberately left untouched (historical record).

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

test/resolvers-gbrain-put-rewrite.test.ts

@@ -0,0 +1,63 @@
+/**
+ * Regression pin: scripts/resolvers/gbrain.ts must emit `gbrain put <slug>`
+ * (the v0.18+ subcommand), never the renamed `gbrain put_page`. The resolver
+ * output ships into every generated SKILL.md file as user-facing
+ * copy-paste instructions; using the old subcommand teaches every
+ * gstack user to invoke a command that no longer exists.
+ *
+ * Two checks:
+ *   1. Resolver source: scripts/resolvers/gbrain.ts has no `put_page`
+ *      tokens in active strings (comments OK — one annotated reference
+ *      explains the rename for future contributors).
+ *   2. Generated SKILL.md: every tracked SKILL.md file is free of
+ *      `gbrain put_page`. Run `bun run gen:skill-docs` if this fails.
+ */
+
+import { describe, it, expect } from "bun:test";
+import { readFileSync, readdirSync, statSync } from "fs";
+import { join } from "path";
+import { execFileSync } from "child_process";
+
+const REPO_ROOT = join(import.meta.dir, "..");
+const RESOLVER_PATH = join(REPO_ROOT, "scripts", "resolvers", "gbrain.ts");
+
+function stripComments(src: string): string {
+  // Strip block comments first (may span newlines, may contain `//`).
+  const noBlock = src.replace(/\/\*[\s\S]*?\*\//g, "");
+  return noBlock.replace(/\/\/[^\n]*/g, "");
+}
+
+function listTrackedSkillMd(): string[] {
+  const out = execFileSync("git", ["ls-files", "*SKILL.md"], {
+    cwd: REPO_ROOT,
+    encoding: "utf-8",
+  });
+  return out.split("\n").filter((line) => line.trim().length > 0);
+}
+
+describe("scripts/resolvers/gbrain.ts — no put_page in emitted instructions (regression for #1346)", () => {
+  it("resolver source ships only `gbrain put` instructions, not the renamed `put_page`", () => {
+    const src = readFileSync(RESOLVER_PATH, "utf-8");
+    const stripped = stripComments(src);
+    expect(stripped).not.toContain("put_page");
+  });
+
+  it("every tracked SKILL.md file is free of the renamed gbrain put_page subcommand", () => {
+    const files = listTrackedSkillMd();
+    const offenders: string[] = [];
+    for (const f of files) {
+      const content = readFileSync(join(REPO_ROOT, f), "utf-8");
+      if (content.includes("gbrain put_page")) {
+        offenders.push(f);
+      }
+    }
+    if (offenders.length > 0) {
+      throw new Error(
+        `Generated SKILL.md files still reference 'gbrain put_page'. ` +
+          `Run 'bun run gen:skill-docs' to regenerate after editing ` +
+          `scripts/resolvers/gbrain.ts. Offenders:\n  - ${offenders.join("\n  - ")}`,
+      );
+    }
+    expect(offenders).toHaveLength(0);
+  });
+});