avoid hardcoded configuration values

Avoid hardcoding configuration values that affect user experience or behavior. Instead, make these values configurable with sensible defaults. This is especially important for timing values, thresholds, and user-facing constants that different users may want to customize.

Examples of values that should be configurable rather than hardcoded:

• Completion trigger thresholds: const MIN_WORD_LEN: usize = 7; should be configurable for users who want completion for shorter words like “because”
• Timing values: const DEBOUNCE: Duration = Duration::from_secs(1); should be configurable as users may prefer faster response times like 20ms
• Default tokens: let token = token.unwrap_or("//"); should use a configurable default comment token rather than hardcoding “//”
• Timeout values: hardcoded timeouts like 30ms should be configurable for testing and different user preferences

When making values configurable:

// Instead of:
const MIN_WORD_LEN: usize = 7;

// Do:
pub struct CompletionConfig {
    pub min_word_length: usize,
}

impl Default for CompletionConfig {
    fn default() -> Self {
        Self {
            min_word_length: 7, // Reasonable default, but configurable
        }
    }
}

This approach improves user experience by allowing customization while maintaining reasonable defaults for users who don’t need to change the settings.