feat: add --memory-limit option for child processes

[Kalipso0505]

Problem

Tools like PHPStan can crash with PHP memory limit: 128M when invoked through phpcstd, because the child processes inherit the default memory_limit from php.ini. Users currently have no way to control the memory limit without modifying PHP configuration globally.

Solution

Adds a -m / --memory-limit CLI option that gets passed to all PHP-based child processes via php -d memory_limit=<value>.

phpcstd --memory-limit=-1      # unlimited memory for child processes
phpcstd --memory-limit=512M    # 512M limit
phpcstd                         # system default (unchanged behavior)

Implementation

• New Cli::PARAMETER_MEMORY_LIMIT constant and CLI option in RunCommand
• Value stored in Context::$memoryLimit, passed to tools via Tool::setContext()
• Tool::execute() prepends php -d memory_limit=<value> to the command when set
• New abstract method Tool::supportsMemoryLimit() forces every subclass to explicitly declare support
• Non-PHP binaries like composer return false to skip the wrapping

Changes

File	Change
Cli.php	New PARAMETER_MEMORY_LIMIT constant
Context.php	New $memoryLimit property
RunCommand.php	Register CLI option, pass context to tools
Tool.php	setContext(), memory-limit logic in execute(), abstract supportsMemoryLimit()
ComposerNormalize.php	supportsMemoryLimit() returns false
All other tools (9)	supportsMemoryLimit() returns true