zsh glob error: 'no matches found' for .pending-* pattern

[stillfox-lee]

Problem

When running gstack skills in zsh, getting this error:

(eval):22: no matches found: /Users/liaosiyi/.gstack/analytics/.pending-*

Root Cause

The Preamble code in every skill contains:
``bash
for _PF in ~/.gstack/analytics/.pending-*; do ...

When no `.pending-*` files exist (which is the common case), zsh errors with "no matches found" because it doesn't handle unmatched glob patterns like bash does.

## Environment
- Shell: zsh
- gstack version: latest (installed from source)
- macOS (likely affects all platforms with zsh)

## Suggested Fix

In `scripts/gen-skill-docs.ts` line 165, change:
``typescript
for _PF in ~/.gstack/analytics/.pending-*; do ...

To:
``typescript
// zsh compatibility: nullglob for missing .pending-* files
(for _PF in ~/.gstack/analytics/.pending-* 2>/dev/null; do ...) 2>/dev/null || true

This wraps the for loop in a subshell with error suppression, making it compatible with both bash and zsh.