Enum ContextTier 

pub enum ContextTier {
    System = 0,
    User = 1,
    KeyTool = 2,
    Assistant = 3,
    RegularTool = 4,
}

消息优先级层级（数值越小优先级越高，用于 window 选择）

• System：始终保留（不计配额）
• User：用户输入，兜底保证最新一条必保留
• KeyTool：承载决策/协议/工作流状态的关键工具，Stage 2 豁免保底
• Assistant：帮手纯文字回复
• RegularTool：常规执行类工具，预算紧张时优先丢弃

Variants

System = 0

User = 1

KeyTool = 2

Assistant = 3

RegularTool = 4

Implementations

impl ContextTier

pub fn priority(self) -> u8

数值形式的优先级（与原 MessageUnit::priority 对齐，越小优先级越高）

Trait Implementations

impl Clone for ContextTier

fn clone(&self) -> ContextTier

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ContextTier

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Ord for ContextTier

fn cmp(&self, other: &ContextTier) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for ContextTier

fn eq(&self, other: &ContextTier) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for ContextTier

fn partial_cmp(&self, other: &ContextTier) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for ContextTier

impl Eq for ContextTier

impl StructuralPartialEq for ContextTier