Writing and design skills: post figures, covers, and grading forecasts

[MaxGhenis]

Adds guidance learned from the 2025 SPM graded prediction post: how posts draw charts and covers, and how a post that grades a forecast should handle the analysis. Three rounds of independent review caught errors in that post's diagnosis, and each rule below comes from one of those catches or from a correction on the post's presentation.

policyengine-writing

New section: Figures, covers and replication in posts

• Charts are ```chart blocks rendered by the website with Recharts and the ui-kit defaults (Design-system bar charts for blog posts; use one in the graded prediction post policyengine-app-v2#1231, #1232). No matplotlib PNGs or Plotly JSON in new posts.
• Newsletter and social images of a chart are screenshots of the live chart, not re-plots.
• Research posts get a photographic still-life cover: teal only in the objects, nothing legible, 1800×840 WebP. The section includes the prompt used for the 2025 SPM posts. Covers are never charts.
• Replication detail goes in footnotes; posts.json dates carry a time of day.

New section: Grading forecasts and explaining misses

• Grade the registered quantity against published margins. When the benchmark change is not significant, reruns show which assumptions matter.
• Every rerun is a full model run.
• Totals come first. Splits depend on the order of the steps, so split each rerun on its own run.
• CPS population controls change between years, so compare per recipient and hold the age mix fixed.
• A pattern needs its sampling error before it is stated as a finding.
• Name rate definitions exactly, and label data series as their source does.
• Get an independent review before publishing.

Writing checklist: four new items covering the above.

policyengine-design

The Charts section now says posts use ```chart blocks, not Plotly. It explains that ui-kit components render unstyled on the website because the site's Tailwind build uses the tw: prefix. The Plotly house style is scoped to notebooks and standalone outputs.

Release

The plugin version goes from 4.0.2 to 4.0.3 in targets/claude/marketplace.template.json and every bundles/*.json.

Checks

uv run pytest --ignore=tests/test_skill_examples.py passes all 178 tests, including the anti-rot lint. The companion app-v2 doc update is PolicyEngine/policyengine-app-v2#1236.

🤖 Generated with Claude Code

[MaxGhenis]

The "Post dates" note added here (skills/policyengine-writing/SKILL.md, the bullet that says to always add a time of day) is obsolete now that PolicyEngine/policyengine-app-v2#1237 has merged: bare dates show as their own day in every time zone. The corrected note is in #95, stacked on this branch and approved by an Opus 5.5 review. Merge #95 into this branch before merging #94, or merge #95 after #94, when GitHub retargets it to main.