perf(goto): lazy load adblock assets

[Kikobeats]

Note

Low Risk
Low risk: this is a localized refactor from eager sync file reads to cached async lazy-loading, with a focused unit test to prevent regressions. Main risk is timing/initialization differences if callers assume immediate availability of the adblock engine or autoconsent script.

Overview
Switches goto adblock initialization to lazy-load heavy assets (engine.bin and autoconsent.playwright.js) via cached promise helpers (getEngine, getAutoconsentPlaywrightScript) instead of readFileSync at module import.

Updates adblock/autoconsent setup to await/chain these loaders when enabling/disabling blocking and when injecting/running the autoconsent script, and adds a unit test that asserts requiring adblock.js performs zero targeted synchronous reads.

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