Make file size messages human-readable

[samdark]

Resolves #802.

Summary

• Format File size placeholders as human-readable values for {limit} and {exactly}.
• Update default File size messages to use the formatted placeholders directly.
• Add regression coverage and document the placeholder behavior.

Tests

• vendor/bin/phpunit tests/Rule/FileTest.php --testdox
• vendor/bin/psalm --config=psalm.xml --output-format=console --no-cache --threads=1
• vendor/bin/php-cs-fixer fix --dry-run --diff --sequential --allow-unsupported-php-version=yes

Full vendor/bin/phpunit was also run; it fails only on existing EmailTest DNS-dependent cases for gmail.com and ñandu.cl domains in this environment.

[Copilot]

Pull request overview

This PR updates the File validation rule to render size-related placeholders ({limit}, {exactly}) as human-readable values (e.g. 50 MB) instead of raw byte counts, and aligns defaults, tests, and documentation with that behavior.

Changes:

• Format {limit} / {exactly} placeholders as human-readable sizes in FileHandler.
• Update default File size messages to use {limit} / {exactly} directly (no ICU number/plural formatting).
• Add regression tests and document the new placeholder behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
src/Rule/FileHandler.php	Formats size placeholders before they’re passed into error message parameters.
src/Rule/File.php	Updates default size messages and placeholder documentation to reflect human-readable sizing.
tests/Rule/FileTest.php	Adds/updates regression cases asserting new human-readable size output.
docs/guide/en/built-in-rules-file.md	Documents that size placeholders are now human-readable.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.