feat(commands): add file tag support for custom command prompts

[fathiraz]

Background

hey @intellectronica! this is a great library, i've been using it in a couple of my projects. however, since this PR #247 about custom commands, i thought about something.

since many IDE/CLI tools have built-in directories for custom commands (not in the rules), i wonder if we can extend this feature so users can use prompt-file instead of only using prompt. i think when we try to add prompts in the TOML, commands that are really long can be hard to write. also, it cannot use markdown for more specific tasks.

so the ideas is to:

• extend custom command configuration to also support prompt_file for specific files
• extend ruler configuration to define where the directory to look for custom command files is, using command_directory configuration
• the command_directory will be excluded from usual ruler process that loads all md files into rules

let me know your thoughts on these changes!

Summary

extend custom commands to support file tag syntax in prompt files, allowing commands to reference and include specific files using tag-based notation (e.g., prompt_file tags).

What's Changed

• add CommandProcessor core module for processing file tags
• update agent interfaces to support command file processing
• integrate file tag resolution in apply-engine
• add comprehensive tests for command propagation and exclusion
• update AbstractAgent and concrete agent implementations

Screenshot