docs: refresh README header, badges and examples

[roxblnfk]

Q	A
Bugfix?	❌
Breaks BC?	❌
New feature?	❌
Issues	—

• README follows the testo layout: RoadRunner logo and tagline, Documentation/Sponsor badges, working quality badges (Psalm level and type coverage via shepherd), a short description, then Get Started → Installation / Usage, followed by the remaining sections.
• Dead badges are gone: Codecov (branch master, no upload in CI), poser and Discord; the License section is removed (the packagist badge links to LICENSE).
• Usage examples now use RoadRunner 2025.x / 3.x versions; added a short note on how the installed version is detected (RR_VERSION, then ./rr --version, cached per process) and a container-less example for a custom binary path.

[coderabbitai]

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