fix(hotkey): 250ms debounce on pressed-edge dispatch

[appergb]

User description

Summary

• 相邻 < 250ms 的 hotkey press 边沿直接丢弃，记 log 方便排查
• 解决：微动开关回弹 / 用户手抖双击 / 用户连点过快 → 空转写报错 + ASR session 抢资源

主要改动

• `coordinator.rs::Inner` 新增 `last_hotkey_dispatch_at: Mutex<Option>` 字段（2 个构造点同步初始化）
• `coordinator/dictation.rs` 加 `HOTKEY_DEBOUNCE = 250ms` 常量，`handle_pressed_edge` 入口检查时间戳

与 `hotkey_trigger_held` 互补：held 防 press-without-release，本检查防 press-release-press 三连过快。用户正常使用（不会快于 4 次/秒）不会触发。

Test plan

• `cargo check --manifest-path src-tauri/Cargo.toml` pass
• CI 三平台 cargo check pass
• 真机：正常切换式录音不受影响（每按一次都生效）
• 真机：故意 50ms 内连按两次，第二下应被 log "debounced" 丢弃

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PR Type

Bug fix

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Description

• Add 250ms pressed-edge debounce

• Drop rapid hotkey repeats

• Initialize dispatch timestamp state

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Diagram Walkthrough

flowchart LR
  A["Pressed hotkey edge"] --> B["250ms debounce check"]
  B -- "too soon" --> C["Log and drop"]
  B -- "accepted" --> D["Route to dictation or QA"]

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File Walkthrough

Relevant files

Bug fix

coordinator.rs Track last hotkey dispatch timestamp                                          openless-all/app/src-tauri/src/coordinator.rs Add last_hotkey_dispatch_at to Inner Document the debounce purpose and scope Initialize the new mutex in both constructors +7/-0      dictation.rs Debounce rapid hotkey press edges                                                openless-all/app/src-tauri/src/coordinator/dictation.rs Define a 250ms HOTKEY_DEBOUNCE constant Check elapsed time before handling pressed edges Update the timestamp only for accepted edges Log debounced presses for easier debugging +24/-0

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[github-actions]

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