implement six-skill gstack 2 runtime

lib/bin-context.ts

@@ -1,19 +1,12 @@
 /**
  * bin-context — tiny shared helpers for non-interactive gstack bins that need the
- * project slug, current branch, and argv flags. Extracted from the decision bins
- * (gstack-decision-log / gstack-decision-search) so the slug/branch/flag plumbing
- * lives in one audited place instead of being copy-pasted per bin.
+ * current branch and argv flags. Project identity is resolved directly through
+ * runtime/identity.js by callers so native Windows never has to execute a
+ * sibling shebang script.
  */
 
 import { spawnSync } from "child_process";
 
-/** Resolve the project slug via the `gstack-slug` helper (parses `SLUG=...`). */
-export function resolveSlug(slugBinPath: string): string {
-  const r = spawnSync(slugBinPath, { encoding: "utf-8" });
-  const m = (r.stdout || "").match(/^SLUG=(.+)$/m);
-  return m ? m[1].trim() : "unknown";
-}
-
 /** Current git branch, or undefined on detached HEAD / outside a repo. */
 export function gitBranch(): string | undefined {
   const r = spawnSync("git", ["rev-parse", "--abbrev-ref", "HEAD"], { encoding: "utf-8" });