fix: restore the 1.4.2 public API

[SNO7E-G]

1.5.0 introduced backward-incompatible changes in a minor release (#628). This restores src/ and tests/ to the 1.4.2 tag verbatim, so the library is behaviourally identical to 1.4.2 for every consumer.

Verification: git diff 1.4.2 -- src is empty. There are no source changes to review.
Restored by reverting rather than by re-implementing:

• untyped public signatures with phpdoc, no native param or return types
• no return type on the RequestMethod::submit() interface
• non-readonly Response and RequestParameters
• the Curl and Socket wrapper classes and their ?Curl / ?Socket dependency-injection constructors, so the documented pattern for testing a custom RequestMethod works again

1.4.2 predates the phpstan level max and php-cs-fixer setup; this repo now runs in CI, and reports 191 pre-existing errors, 62 of them in src/. Many of those, such as offset access on mixed and resource parameters, cannot be resolved with annotations alone. Changing code in a revert would defeat the purpose of the revert, so they are recorded in phpstan-baseline.neon instead. The follow-up hardening removes entries from it as it adds the guards that fix them. php-cs-fixer needed no changes to the 1.4.2 sources.

phpunit 52 passing, phpstan clean against the baseline, php-cs-fixer clean.

[acoulton]

@SNO7E-G thanks for this - I've reviewed git diff 1.4.2..SNO7E-G/fix/restore-1.4.2-public-api and it looks correct to me.

There are changes to examples files that were after 1.4.2 but before / separate to the code changes, and the changes to the CI / phpstan config, I agree that it's appropriate to keep those and to add the phpstan baseline to resolve the warnings.

@rowan-m if you're happy with this would it be possible to get it merged and released as 1.5.1 to fix the issues with 1.5.0, and as a baseline for future improvements?