Command surface: adopt, merge, and add metadata

[UltraBob]

Adopt commands from ddev-module-developer, implement the merged command surface, remove --preview, and add metadata headers to all commands.

Work items

• Adopt phpunit, rector, phpmd, phpcompat, core-js-install
• checks: CI job order, allow-failure warnings, per-tool report logs
• checks --bonus for phpmd and phpcompat
• checks-fix with checks-fixes alias; individual *-fix commands stay
• checks-full: discover and run unit tests
• Remove --preview from eslint-fix and prettier-fix, failing loudly
• php-parallel-lint canonical, parallel-lint aliased
• Add ## Description:, ## Usage:, ## Example:, ## ExecRaw: to all commands

Acceptance criteria

• All adopted commands available
• checks runs in CI job order with allow-failure warnings
• checks --bonus includes phpmd and phpcompat
• checks-full discovers and runs unit tests
• --preview removed; flag produces error message
• All commands have metadata headers

Blocked by: ADRs for command surface and preview removal (PRs pending)