Commit 6fda452e77

Messier objects on the sky chart (!57)

Messier objects on the sky chart, after batching the star fills.

## Star fills (94af22b)
`SkyView.drawStars` now builds one path per bin (half a magnitude × four B−V tints, 72 bins) and fills each once, faintest first. Each star keeps its own radius. Colour and opacity are within 0.25 mag and 1/6 tint of the per-star values (`starBinsStayCloseToEachStar`).

Timings: `ImageRenderer` on an Apple silicon Mac, Chicago 2026-10-17 02:00 UT, 393×852 pt at 3× (1179×2556), default view, 8,404 stars. "Canvas" is the time spent in the Canvas closure (`onDraw`). Each figure is the median of 100 renders after 10 warm-up renders; the range covers 3 runs.

| | before | after batching | after, Messier layer on |
|-|-|-|-|
| debug, canvas, day | 2.7–2.8 ms | 2.1–3.2 ms (min 2.0) | 2.5–3.1 ms (min 2.1) |
| release, canvas, day | 1.3–1.4 ms (min 1.2) | 0.8–0.9 ms (min 0.6) | 1.7–2.0 ms (min 0.6) |
| release, canvas, night | 1.1–1.2 ms (min 1.0) | 0.7–0.8 ms (min 0.6) | 1.2–2.4 ms (min 0.7) |
| scene build, release | 1.0 ms | 1.0 ms | 1.1–2.0 ms |

The first render in a fresh process (`renderStaticSky`, the figure M0 used) is 50–180 ms both before and after, and is mostly one-time setup. The "Messier layer on" runs overlapped with builds in other worktrees: their medians are noisy, so compare the minimums.

## Data (1e35a36)
`scripts/make-messier.py` fetches OpenNGC at tag v20260501 (NGC.csv and addendum.csv) and writes `SkyRenderer/Resources/messier.json` (13 KB, 109 objects). Each object has its J2000 RA/Dec in degrees, OpenNGC type, magnitude (V, else B), major and minor axes in arcminutes, position angle, and its Library page id, taken from `link.messier` in `deep-sky-*.json`. OpenNGC lists M102 as a duplicate of M101, so M102 is left out. The M102 Library page keeps its own text ("probably the Spindle Galaxy") and is not linked from the chart. THIRD_PARTY.org and Settings > Credits now credit OpenNGC under CC BY-SA 4.0. The repo is public, so the converted file is also available without DRM.

## Chart (699b77a)
- `DeepSkyObject`, `Catalog.deepSky`, `SkyScene.deepSky`. The scene places each object and a point 0.1° north of it in one batch call. Symbols are oriented from that north point. A test checks that the east direction matches a projected point east of the object.
- Symbols are stroked in `style.line` at 0.8 pt and drawn between stars and bodies. A symbol is drawn at the object's true size, with a minimum radius of 4 pt:
  - galaxy (G): ellipse at its position angle
  - open cluster (OCl, plus M24, M40 and M73): dashed circle
  - globular (GCl): circle with a cross
  - nebula (Neb, HII, RfN, Cl+N, and SNR for M1): square
  - planetary nebula (PN): small circle with four ticks
- "M31"-style labels appear at a field of view of 60° or less. At 90° the labels pile up in Sagittarius.
- `SkyObject.deepSky(Int)`. A tap hits a Messier object within 0.6 × the tap radius, after bodies and before constellations.
- Tapping a symbol opens a card with the Library subtitle, altitude, direction, magnitude and size, plus Log and Read more (the Library page).
- Toggle: Settings > Display > Messier objects, on by default (`SettingsKey.showDeepSky`). It hides both the symbols and their hit test.

## Not verified
- Draw time on a real iPhone.
- The card, the toggle and the chart in the running app. The app builds for the iOS simulator, but I could not boot a free simulator (process limit). The symbols were checked only in `ImageRenderer` PNGs from the package tests.
- Tours do not point at Messier objects (`Tour.Target.messier` is not added).

Layout: unified · split