Fix remote SVG bundling and non-interactive image rendering tests

[itsfuad]

imgbundler/png/xgif: fix nondeterministic remote SVG bundling and non-interactive render paths

Summary

This fixes three issues that were showing up across CI and local runs:

• normalize remote SVG responses before embedding so output does not depend on CDN transfer encoding
• avoid Chromium install prompt failures in non-interactive test runs
• fix GIF frame generation for short animation intervals

Changes

• lib/imgbundler

  • decode Content-Encoding for remote image responses before embedding
  • add regression coverage for compressed remote SVG responses

• lib/png

  • auto-install Playwright/Chromium when stdin is not a TTY instead of prompting

• lib/xgif

  • fix frame count calculation for short durations
  • fix frame delay handling so static and animated paths preserve intended timing
  • add regression coverage for frame count and delay logic

• e2etests-cli

  • update the chain_icon_import golden output to match normalized embedded SVG content

Root Cause

chain_icon_import was flaky because we were embedding raw remote response bytes for SVG icons. When the server returned compressed content, snapshots could differ by environment even when the SVG itself had not changed.

Local go test failures with failed to read user input: EOF came from prompting for Chromium installation in a non-interactive process.

GIF failures came from integer division in frame count calculation, which could produce 0 frames for short intervals such as 10ms.

Verification

• GOTOOLCHAIN=go1.25.0 go test ./lib/imgbundler ./lib/xgif -count=1
• GOTOOLCHAIN=go1.25.0 go test ./e2etests-cli -count=1
• COLOR=1 ./make.sh

Screenshots

• N/A