fix: inset mac app icons onto the macOS icon grid

[shannah]

What this fixes

An installed jDeploy app's icon renders visibly larger than the apps beside it in the command-tab switcher, the Dock and Mission Control.

Apple's macOS icon template centres an 824×824 body in a 1024×1024 canvas — every icon macOS draws next to ours leaves that margin. jDeploy wrote the source artwork into every icns slice edge to edge, so at the same slot size it renders ~24% wider (1024/824) than its neighbours.

Why it showed up now

Before #475, macOS treated the single-slice icns as legacy and shrank it onto a plate — that supplied a margin by accident. With the full slice family in place macOS draws the artwork as authored, so a full-bleed source now shows at full slot width. #479 fixed the small-slice scrambling but not the size, which is why the icon came back uncorrupted and still oversized.

Approach

MacBundler.writeIcns now runs the source through fitToIconGrid before cutting slices:

• The artwork is measured by its opaque bounds, not by the canvas, so an icon already authored to Apple's template is passed through untouched, and one carrying part of the margin is scaled the rest of the way rather than twice over.
• Only sources that reach past the grid (plus a 2% tolerance) are re-composited; the scale/centre is done once at full canvas resolution with bicubic resampling, and every slice is cut from that.
• Sources too small to fill any slice we emit keep their single native slice unchanged — insetting artwork that small would leave nothing of it.
• Non-square, unreadable and fully transparent sources are left alone.
• The intermediate icon-grid.png matches the existing thumbnail cleanup pattern, so it is removed with the rest.

Measured on jDeploy's own default icon.png (512×512, full bleed): artwork now spans 409×412 of the 512 canvas ≈ 80.1%, against 512×512 (100%) before.

Testing

MacBundlerIconTest gains three cases; all 237 shared-module tests pass.

• insetsFullBleedArtworkOntoTheIconGrid — fails on the pre-fix code (expected: <824.0> but was: <1024.0>), and also checks the artwork is centred.
• leavesArtworkThatAlreadySitsOnTheGridAlone — a 700-of-1024 source comes through at 700.
• removesTheGridFittedSource — no leftover intermediate.

Delivery

The fix is in shared, so it reaches an installed .app through whichever component builds that bundle — the CLI at publish time for prebuilt platform bundles and for the local install paths, or jdeploy-installer when the installer builds the bundle on the end user's machine. The installer-built route tracks its own npm release rather than the CLI's: jdeploy-installer@latest is 6.1.5, whose MacBundler still has the pre-#475 single-slice createThumbnails(File, File), so that route only picks this up once a release carries it.

🤖 Generated with Claude Code

https://claude.ai/code/session_0133NB1qceV5MzfvRzdVPxm5