feat: image-gen ×11 factory pages (eval + images)

[joesmart]

Summary

• Ship image-gen ×11 factory pages under prompts/image-gen/.
• Each public page is a cleaned eval report with inline generated images (images/*.png).
• synthetic_codex fixtures embed both MAIN-synthetic + B.
• Root README.md: add prompts/image-gen/ to the directory table + section 「已出厂（2026-09-14 图片批）」.
• Tagline kept: 没跑过 = 不出厂.

Factory checklist

• Four gates true (gate_complete/traceable/safe/one_pass)
• Prompt text verbatim in code blocks
• Images embedded via relative ![](images/...)
• synthetic: MAIN-synthetic + B both present
• No secrets / no private vault paths (Documents/obsidian, 20_Projects/..., 60_Templates/..., herdr session internals)
• No Inbox half-finished pages
• Obsidian wiki links rewritten to relative markdown

Risk

低 — content + assets only; no workflows/secrets/force-push.

Test plan

• Spot-check 1 official page (e.g. GPTImage25-龙武士草原对峙.md) renders B image on GitHub
• Spot-check 1 synthetic page (e.g. GPTImage2-对半编辑艺术海报.md) renders MAIN-synthetic + B
• Confirm root README lists the 2026-09-14 image batch and directory table includes prompts/image-gen/