Remove Loader as a top-level package and split its responsibilities across Config, Environment, and helper boot

Summary

Refactor the current Loader package out of the top-level framework architecture.

Its responsibilities should be split into the places that actually own them:

• hierarchical config file resolution should belong to Config
• environment bootstrap file resolution should belong to Environment
• helper loading should be handled separately and should not justify Loader remaining its own package

Why

Right now Loader acts like a standalone package, but the code shows it is mostly a shared utility for unrelated internal concerns.

Current usages include:

• Config loading hierarchical config files
• Environment loading env bootstrap config
• UploadConfigProvider probing/loading optional uploads config
• helper directory loading during boot

This is a weak package boundary.

The most obvious mismatch is Environment: environment bootstrap should not depend on a separate generic loader package just to resolve a small config file that determines which .env file to load.

Current Behavior to Preserve

For config loading, preserve the current hierarchical resolution behavior:

• resolve the module-scoped file first
• if the setup is hierarchical and the module file does not exist, fall back to the shared file

For config imports that currently means:

• modules/<module>/config/<file>.php
• then shared/config/<file>.php

Proposed Changes

• remove Loader as a standalone top-level package concept
• move hierarchical config file resolution into Config
• move environment bootstrap file resolution into Environment
• update UploadConfigProvider so its optional config lookup follows the new ownership boundaries
• keep helper loading as a separate concern and do not let it define the long-term architecture of Loader

Acceptance Criteria

• Loader is no longer treated as a standalone top-level package
• Config owns hierarchical config file resolution
• Environment no longer relies on Loader for its bootstrap config resolution
• UploadConfigProvider no longer relies on a generic top-level loader abstraction if a more local ownership model is available
• existing hierarchical config behavior remains compatible
• tests and docs are updated as needed

Notes

Relevant code:

• src/Loader/Loader.php
• src/Loader/Setup.php
• src/Config/Config.php
• src/Environment/Environment.php
• src/Storage/Uploads/UploadConfigProvider.php
• src/App/Stages/LoadHelpersStage.php

Start by tracing the responsibilities and usages across src/Loader/Loader.php, src/Loader/Setup.php, src/Config/Config.php, src/Environment/Environment.php, src/Storage/Uploads/UploadConfigProvider.php, and src/App/Stages/LoadHelpersStage.php. Verify the existing hierarchical resolution behavior and identify the tests and docs affected before separating ownership. Done means Loader is no longer a top-level package, the new owners preserve compatible behavior, and tests and docs are updated as needed.