Observable Plot for charts; story

A session that got the drafting work for v1 done: settled the charting tool, finished the story #2 draft, applied the structure benchmark's findings, ran a first enrich rep, and wrote first drafts of both the story and enrich skills. Also trimmed a NEXT.md that had grown into a second backlog.

Charting: Observable Plot. The near-term half of #11 is decided. The line-charts bake-off rates Plot the best chart-per-line-of-code for a data story, and both hand-written stories' friction notes pointed the same way — story #2's normalised ranged-bar scoreboard was about the ceiling of what hand-rolled inline SVG is comfortable for. docs/charting.md records the decision and the pattern: Plot authored in a *-make-charts.mjs, rendered to static SVG in Node (jsdom for the DOM), committed and embedded as a Markdown image — no JavaScript on the published page, same deployment as before. Build-only dependencies live in a scoped site/stories/package.json, the same convention as a dataset's build.ts deps. planetary-boundaries-make-charts.mjs is the reference — ~45 lines for the scoreboard against ~120 hand-rolled, with byte-identical output across runs. The side-by-side that settled it is shipped at site/charting-spike.html. The longer half of #11 — a DataHub/Flowershow-native views standard — stays deferred. The Keeling Curve charts (story #1) stay hand-rolled until touched (#12).

Data story #2 drafted. Planetary Boundaries: the outline + chart plan were committed on 2026-09-05; this session added the two charts and the prose, each its own commit, the #10 way. The scoreboard needed a modelling call the outline's chart plan didn't survive: current ÷ boundary is undefined for novel entities (boundary = 0) and wrong-signed for the "less is worse" indicators, so it uses the framework's own normalisation instead — (current − pre-industrial) / (boundary − pre-industrial), boundary = 1×. Six of nine boundaries crossed; the counter-note is stratospheric ozone, dipping toward the boundary through the twentieth century and recovering after the Montreal Protocol. Left: the author's "sounds like me" voice pass. #4.

structure benchmark findings applied. All eight edits from docs/structure-benchmark.md (benchmark v1, 2026-09-05) landed. In scripts/wrangling-idioms.mjs (tests 24 → 28): excelSerialToIsoDate() — an offset-free Excel-serial → ISO date converter, because reading a spreadsheet date through a JS Date shifts it a day in positive-UTC zones and silently turned 1987-05-20 into 1987-05-19 in the oil-prices build; num(raw, sentinels) — a strict numeric parser with a per-column "no data" sentinel list; and toCsv() upgraded to real RFC 4180 quoting. In skills/structure/SKILL.md: exceljs vs SheetJS xlsx for legacy .xls, the timezone-naive-date rule, naming conventions vs a published dataset, LF line endings with no Frictionless dialect block, and a "build needs a dependency ⇒ its own package.json" section. AGENTS.md picked up the exceljs/SheetJS split and the dependency rule.

story skill — first draft. skills/story/SKILL.md, from the two hand-made stories plus the craft docs (story-craft.md, voice-guide.md, charting.md). It is the workflow — three committed, independently reviewable artefacts (outline + chart plan → charts → prose), the outline template lifted from the two stories, a definition of done, and the "sounds like me" voice pass kept as a separate human stage — and it references the craft docs rather than restating them. Deliberately not symlinked into .claude/skills/: it is there for review, not activation, until it has been run on a real story (#10).

enrich skill — first draft, after one hand rep. The rep: enrich.ts

• SUMMARY.md for co2-ppm — a reproducible zero-dependency stats script (per-resource n / missing / min / max / mean / median / std dev, skipping time-encoding identifier columns) that rewrites only a fenced block in SUMMARY.md, plus a hand-written "What stands out" (the Mauna Loa uncertainty columns are constant and carry no information; the growth rate is never negative; the rise is accelerating; two decadal rows are partial) and "See also". status bumped structured → enriched. The skill (skills/enrich/SKILL.md) generalises that: enrich.ts + fenced SUMMARY.md + one to three declarative views for first charts (not Observable Plot SVGs — those stay a story's job) + the status bump. Also DRAFT, also unsymlinked, pending a second rep (oil-prices, to settle how parallel same-schema resources are summarised).

NEXT.md trimmed; roadmap moved to an epic. The "Roadmap to v1" arc and a growing "Already done" log had turned NEXT.md into a second backlog plus a duplicate changelog. The five-step arc is now epic #14; NEXT.md is back to a short pointer. site/README.md's status and roadmap sections, stale since before the benchmark, were refreshed to match.