feat(cursor): optional per-device usage via Agent hooks - #699

Summary

• 增加可选的 Cursor 按设备用量采集（Agent hook → 本机 jsonl），默认仍走账号级 CSV
• device 模式下不再跑 tokscale cursor sync，避免和账号总量叠算
• Limits 仍按账号；ingest 形状不变，现有按设备展示就能用上
  对应 希望 Cursor 用量也能按设备显示（多设备 Hub 目前会把同一账号加总） #698。先开草案，等 issue 方向确认后再转 Ready。

Test plan

• npm run verify
• 打开「仅统计本机 Cursor 用量」后，本机 Agent 对话会写入 jsonl，且不再跑 cursor sync
• 关掉开关后恢复账号级 CSV，且只移除我们自己的 hook
• 未打开开关时行为和现在一致

Summary by cubic

Adds an opt-in per-device Cursor usage mode that records Agent stop hooks into a machine-local jsonl, so a Hub no longer sums the same account CSV on every device. Default remains account-level CSV.

Summary

• New cursorUsageSource setting (account default | device), exposed as the Settings → Cursor "Count Cursor usage on this device only" checkbox and the TOKEN_MONITOR_CURSOR_USAGE_SOURCE env var.
• Device mode installs a Cursor Agent stop/subagentStop hook into ~/.cursor/hooks/ and appends token counts to <sharedDataDir>/cursor-device/usage.jsonl, overridable via TOKEN_MONITOR_CURSOR_DEVICE_LOG.
• Hook command paths are quoted with forward slashes so Windows installs do not break on escaping.
• Device mode skips tokscale cursor sync and treats Cursor as a runtime-local adapter, so account totals are not double-counted; limits stay account-scoped.
• The device jsonl directory is watched while the tokscale cache is not, so the self-trigger loop (issue macOS：并发 tokscale 扫描可能拖垮 syspolicyd，导致 Gatekeeper 返回 Too many open files #15) does not return.
• Inclusive input_tokens are split so cache read/write is not double-counted by tokenValue().
• Switching back to account mode removes only our hook marker and preserves unrelated hook commands.
• Cloud Agent usage is not recorded.
• Branch kept current with upstream v0.60.0, including the Cursor legacy-session fix.

Tests and risks

• New unit tests cover hook install/uninstall (including Windows path quoting), device usage parsing, and collector integration; npm run verify passes.
• Device mode requires the Cursor config directory to exist; hook install fails open and only logs an error otherwise.
• The hook script uses only Node built-ins so the copied file runs without the rest of the app.
• Draft pending direction on issue 希望 Cursor 用量也能按设备显示（多设备 Hub 目前会把同一账号加总） #698.

^{Written for commit 840e3d3. Summary will update on new commits.}