Fix missing icon-16.png causing Chrome extension load error

[Copilot]

manifest.ts references icon-16.png in both icons and web_accessible_resources, but the file was excluded via .gitignore and never committed, causing Chrome to log: "Couldn't load icon icon-16.png specified in icons."

Changes

• Added chrome-extension/public/icon-16.png — 16×16 PNG generated by downscaling icon-128.png with Lanczos resampling
• Removed chrome-extension/public/icon-16.png from .gitignore — the file was previously blocked from being tracked

How to check the feature

Load the unpacked extension in Chrome (chrome://extensions → Load unpacked → dist/). Confirm no console warning about icon-16.png appears, and the 16px icon renders correctly in the browser toolbar/extensions page.

Reference

manifest.ts icon declaration:

icons: {
  128: 'icon-128.png',
  34:  'icon-34.png',
  16:  'icon-16.png',   // was missing from repo
},

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