Adds support for custom tools - user-defined functions that the LLM can
call during conversations. Custom tools work alongside opencode's built-in
tools and are configured through the new `tools` option.
The configuration follows the same pattern as other opencode settings like
`agents` and `commands`, supporting:
- Inline TypeScript content
- Individual file paths
- Bulk directory imports
The `commands`, `agents`, and `themes` options now accept either an
attribute set (existing behavior) or a path to a directory containing
multiple files. When a directory path is provided, it is symlinked to
the appropriate `$XDG_CONFIG_HOME/opencode/` subdirectory.
This change aligns with the existing `skills` option implementation and
provides a more convenient way to manage multiple configuration files
without needing to define each one individually in Nix.
Include various tests for the agents and command file generation and
different ways of configuring it.
Signed-off-by: Austin Horstman <khaneliman12@gmail.com>
