Add YAML config for watch targets and runtime defaults

[melonattacker]

Is your feature request related to a problem? Please describe.

Currently, logira supports YAML files only for detection rules via:

--rules <yaml-file>

There is no persistent configuration for:

• watch targets
• run defaults
• runtime behavior

As new features such as watch mode and run modes are introduced, a configuration system would help users manage settings more easily.

Describe the solution you'd like

Add YAML configuration support.

Example:

watch:
  targets:
    - claude
    - codex
    - cursor
  linger_after_exit: 60s
  idle_timeout: 5m

run:
  default_mode: strict-run
  summary: detections

output:
  color: auto

Describe alternatives you've considered

Users could continue specifying all options via CLI flags.

However, this becomes inconvenient when repeatedly configuring the same behavior (especially for watch targets).

Another alternative would be environment variables, but YAML provides better structure and extensibility.

Additional context
This configuration system could later support:

• notification integrations
• advanced watch rules
• runtime tuning options

but the initial version can remain simple and focused on watch targets and run defaults.