docs: streamline README quickstart section

[Copilot]

The “Get started fast” block in the README was overly long and duplicated details better covered in the Quick start doc.

• Quickstart trim: Reduced the section to prerequisite, one-line install, and first command; kept Copilot one-liner.
• De-duplication: Pointed readers to docs/quickstart.md for checksum, version pinning, and manual install details.
• Clarity: Retained cosign verification reference; removed redundant install variants and verbose checks.

Example snippet now shown:

curl -sSL https://raw.githubusercontent.com/githubnext/gh-aw-firewall/main/install.sh | sudo bash
sudo awf --allow-domains github.com -- curl https://api.github.com

Original prompt

unbloat Get started fast in README

Custom agent used: technical-doc-writer
AI technical documentation writer for awf library using Astro Starlight

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[github-actions]

Test Coverage Report

Metric	Coverage	Covered/Total
Lines	81.02%	1230/1518
Statements	80.98%	1261/1557
Functions	78.16%	136/174
Branches	72.56%	410/565

Coverage Thresholds

The project has the following coverage thresholds configured:

• Lines: 38%
• Statements: 38%
• Functions: 35%
• Branches: 30%

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Coverage report generated by `npm run test:coverage`