Clippy Lint Compliance Required

This rule applies to files matching the patterns above.

# Clippy Lint Compliance Required

## Rule
All Rust projects MUST pass `cargo clippy` with zero warnings. Library crates SHOULD enable pedantic lints. Configure lint levels in Cargo.toml, not with scattered allow attributes.

## Format
```toml
# Cargo.toml
[lints.clippy]
pedantic = { level = "warn", priority = -1 }
nursery = { level = "warn", priority = -1 }
# Allow specific lints with documented reasons
module_name_repetitions = "allow"
must_use_candidate = "allow"
```

## Good Examples
```toml
# Cargo.toml — centralized lint configuration
[lints.clippy]
pedantic = { level = "warn", priority = -1 }
# Specific overrides
module_name_repetitions = "allow"
missing_errors_doc = "allow"
missing_panics_doc = "warn"
unwrap_used = "deny"
expect_used = "warn"
```

```rust
// Code that satisfies Clippy pedantic

// Use if let instead of match with single arm
if let Some(value) = optional {
    process(value);
}

// Use map/unwrap_or instead of match
let name = user.name.as_deref().unwrap_or("Unknown");

// Explicit return types on public functions
pub fn calculate_total(items: &[Item]) -> Result<f64, CalculationError> {
    items
        .iter()
        .map(|item| item.price * f64::from(item.quantity))
        .try_fold(0.0, |acc, price| {
            if price.is_finite() {
                Ok(acc + price)
            } else {
                Err(CalculationError::InvalidPrice)
            }
        })
}
```

## Bad Examples
```rust
// BAD: Blanket allow to silence warnings
#![allow(clippy::all)]

// BAD: Using unwrap in library code
let value = map.get("key").unwrap();  // Panics on missing key

// BAD: Needless pass by value
fn process(data: Vec<String>) { ... }  // Should be &[String]

// BAD: Using clone unnecessarily
let name = user.name.clone();  // Borrow instead if possible
```

## Enforcement
- CI: `cargo clippy -- -D warnings` (deny all warnings)
- Pre-commit hook: `cargo clippy --all-targets`
- Configure lint levels in Cargo.toml, not source files