feat(skills): add vibe-aesthetic — design evaluation capture + LLM prompt

[HermeticOrmus]

Why

New skill in the vibe-* family for design evaluation. Where vibe-explore maps what a page lets you do and vibe-recon maps the auth wall, vibe-aesthetic asks what does this page feel like, and where is it weak?

Captures evidence (section screenshots at desktop + mobile, design-token probe), then renders an LLM-agnostic evaluator prompt that any host LLM can read to score the page across nine dimensions and produce an AESTHETIC.md deliverable.

Use cases the skill is built for:

• Pre-launch design review on a deployed site
• Post-rebrand verification — did the new identity actually land?
• Variant comparison — score two candidates on the same rubric
• Brand-family coherence — score sibling sites and see who's lifting / dragging

What changed

New skill bundle at skills/vibe-aesthetic/:

• SKILL.md — entry brief, pipeline, daemon-hygiene notes
• aesthetic.sh — runner (prep + walk + prompt render)
• walk.sh — section-aware walker with auto-anchor discovery, viewport-stepped fallback when no <section id> elements exist
• probe.js — design-token probe (palette frequencies, typography, surface tokens, composition counts, meta). Returns JSON.stringify(...) so it serializes cleanly through vibium eval --stdin
• prep.sh — daemon hygiene enforcing --headless to prevent silent 0-byte captures on SSH/CI sessions with empty DISPLAY
• PROMPT.md — LLM-agnostic evaluator template with rubric, score anchors, output spec, and discipline notes
• examples/reference-run.md — anonymized 8-iteration trajectory (7.4 → 9.5) documenting realistic score movement, the code ceiling at ~8.7, and the photography-as-ceiling pattern

How to test

From the repo root after building vibium:

make build-go
mkdir /tmp/aesthetic-test
skills/vibe-aesthetic/aesthetic.sh /tmp/aesthetic-test https://example.com/ --quick --viewport desktop

Expected:

• /tmp/aesthetic-test/sections/s00_top__desktop.png etc. exist and are non-zero
• /tmp/aesthetic-test/probes/tokens_desktop.json parses as valid JSON
• /tmp/aesthetic-test/PROMPT.filled.md contains the rubric + screenshot list + probe JSON
• /tmp/aesthetic-test/RUN.md has the run summary

For a fuller test against a real multi-section page (auto-anchor discovery exercised):

skills/vibe-aesthetic/aesthetic.sh /tmp/aesthetic-full https://news.ycombinator.com/ --viewport desktop

Notes

• The skill is read-only by construction — no login required for public pages, no destructive surface.
• The shipped PROMPT.md template is editable — operators can retune the rubric (different dimension set, different acceptance bar, different domain register) without changing the capture pipeline.
• The daemon-headless lesson in prep.sh was discovered in the field — without it, every capture command logs success but writes nothing. Worth documenting upstream so future skill authors don't repeat the pattern.
• Tested against example.com (single-fold fallback path) and a real multi-section deployed site (auto-discovery captured 4 anchored sections plus top + bottom).