fix: enforce Codex 1024-char description limit + auto-heal stale installs (v0.11.9.0) (#391)

* fix: enforce 1024-char Codex description limit + auto-heal stale installs

Build-time guard in gen-skill-docs.ts throws if any Codex description
exceeds 1024 chars. Setup always regenerates .agents/ to prevent stale
files. One-time migration in gstack-update-check deletes oversized
SKILL.md files so they get regenerated on next setup/upgrade.

* chore: bump version and changelog (v0.11.9.0)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

test/helpers/codex-session-runner.ts

@@ -27,6 +27,7 @@ export interface CodexResult {
   durationMs: number;       // Wall clock time
   sessionId: string | null; // Thread ID for session continuity
   rawLines: string[];       // Raw JSONL lines for debugging
+  stderr: string;           // Stderr output (skill loading errors, auth failures)
 }
 
 // --- JSONL parser (ported from Python in codex/SKILL.md.tmpl) ---
@@ -167,6 +168,7 @@ export async function runCodexSkill(opts: {
       durationMs: Date.now() - startTime,
       sessionId: null,
       rawLines: [],
+      stderr: '',
     };
   }
 
@@ -282,6 +284,7 @@ export async function runCodexSkill(opts: {
       durationMs,
       sessionId: parsed.sessionId,
       rawLines: collectedLines,
+      stderr,
     };
   } finally {
     // Clean up temp HOME