fix: address pending PR review follow-ups

[BobDLA]

Summary

• add Firefox data_collection_permissions.required = ["none"] and enforce it in release artifact checks
• harden AGENT-CHROME-010 by skipping targeted topic links and waiting for refresh completion instead of sleeping a fixed interval
• extend drawer scroll containment and Firefox scrollbar styling to inner scrollable containers
• sync AGENTS/testing docs with the stronger Firefox artifact check

Why

This PR addresses still-valid automated review feedback left on earlier PRs:

• PR feat: add Firefox packaging trial #5: missing Firefox AMO consent metadata
• PR test: add refresh smoke coverage #7: flaky refresh smoke due to targeted links and fixed sleep
• PR fix(drawer): 自定义抽屉滚动条样式并阻止滚动穿透至外部页面 #8: inner scroll containers could still chain scroll to the page, and Firefox styling should cover the relevant drawer scrollers

Validation

Tier 0

• bash scripts/check.sh
• bash -n scripts/agent-smoke.sh

Tier 1

• bash scripts/build-release-artifacts.sh v0.0.0-local /tmp/linux-do-sidepeek-dist-pr-review
• bash scripts/check-release-artifacts.sh /tmp/linux-do-sidepeek-dist-pr-review/linux-do-sidepeek-0.0.0-local-chrome.zip /tmp/linux-do-sidepeek-dist-pr-review/linux-do-sidepeek-0.0.0-local-firefox-unsigned.xpi

Tier 2

• not run: current live Chrome session was loading a different unpacked worktree, so the result would not have been trustworthy

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