Make README the project front door

[scottdensmore]

Summary

• add an optimized panoramic hero illustration for the project
• reduce the README to a concise front door with quick-start and documentation navigation
• add focused getting-started, architecture, and language-reference guides
• move release maintenance guidance into the contributor guide
• point compatibility documentation at the language reference as the behavior source of truth

Why

The README was accurate but combined onboarding, usage, language details, development commands, layout, and release maintenance in one page. This makes the repository easier to scan while preserving and expanding the technical material in documents with clear ownership.

User and developer impact

Users get a shorter entry point, clearer installation and CLI guidance, and a detailed supported-language reference. Contributors get an implementation-backed walkthrough of the source-preparation, lexer, parser, AST, and evaluator pipeline. Product behavior is unchanged.

Validation

• all local Markdown links resolve
• hero image decoded at 2172x724 and was optimized from 1.8 MiB to 252 KiB
• documented CLI version and sample output matched the built executable
• git diff --check
• make check — vet, race tests, 82.9% coverage, zero lint issues
• make fuzz
• make build
• make release-check VERSION=docs
• make corpus-smoke — all 112 byte-distinct variants passed
• make vuln — no vulnerabilities found