test(ci): harden Karma browser tests against launch flakiness under allTests

[michalharakal]

Problem

allTests (run on every CI PR/push, and locally) intermittently fails a browser test with:

Errors occurred during launch of browser for testing. - ChromeHeadless
> ...the test task did not discover any tests to execute.

This surfaced as :skainet-data:skainet-data-api:wasmJsBrowserTest failing during a full allTests run, while the same task passes every time in isolation.

Root cause

Not a test bug — a flaky browser launch under concurrency. allTests starts ~20 wasmJs/js *BrowserTest tasks at once, each spinning up its own ChromeHeadless. On a loaded machine a browser exceeds Karma's default capture/activity timeouts (Disconnected, no message in 30000 ms / ChromeHeadless was not killed), Karma drops it, reports zero discovered tests, and Gradle fails the build on its failOnNoDiscoveredTests check. CI is the worst case for this: ubuntu-latest, -Xmx4g, and PRs run clean assemble allTests so every browser test re-executes from scratch.

Fix

Add a karma.config.d/skainet-browser-resilience.js to every browser-test module (the Kotlin Gradle plugin merges these into the generated karma.conf.js). It raises the capture/disconnect/no-activity timeouts and adds disconnect tolerance, so a CPU-starved browser is waited on instead of abandoned:

config.set({
    captureTimeout: 120000,
    browserDisconnectTimeout: 30000,
    browserDisconnectTolerance: 3,
    browserNoActivityTimeout: 120000,
    pingTimeout: 120000,
});

These knobs are not exposed by Kotlin's useKarma {} Gradle DSL, so a karma.config.d/*.js file is the supported way to set them. Applied across all browser modules (23 files) so the flakiness can't simply hop to a different module on the next run.

Verification

./gradlew allTests --rerun-tasks — forced every test task (incl. all browser tasks) to actually re-execute concurrently rather than hit the cache. BUILD SUCCESSFUL in 2m41s, no failures, no "did not discover any tests", no browser launch errors.

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