feat: add unified session timeline, main-thread blocking watchdog, and graceful Zone fallback

[AmisKwok]

Summary / 摘要

Add a unified session timeline and a main-thread blocking watchdog, and make runAppWithInspector degrade gracefully instead of crashing on a pre-initialized binding. / 新增统一会话时间线与主线程阻塞看门狗，并让 runAppWithInspector 在 binding 已初始化时优雅降级而非崩溃。

Changes / 变更

• Unified session timeline (TimelineViewer) merges network / logs / errors / routes / alerts into one time-ordered stream, with per-source filtering and a ±N-second focus-around-any-event mode (TimelineService). It sits after the Routes tab and before the Widgets tab. / 统一会话时间线（TimelineViewer）把网络 / 日志 / 异常 / 路由 / 告警归并为一条时间流，支持逐来源筛选与「聚焦任意事件前后 ±N 秒」模式（TimelineService）；Tab 位于 Routes 之后、Widgets 之前。
• Main-thread blocking watchdog (BlockingWatchdogCard in the FPS tab) detects UI-isolate stalls invisible to FPS via a 100ms heartbeat (off by default, own switch). / 主线程阻塞看门狗（FPS 页内 BlockingWatchdogCard）用 100ms 心跳捕捉 FPS 看不见的 UI isolate 卡死（默认关闭、独立开关）。
• runAppWithInspector no longer throws "Zone mismatch" when the binding was pre-initialized; it degrades to a plain runApp (debugPrint still captured). / runAppWithInspector 在 binding 预初始化时不再抛 "Zone mismatch"，降级为普通 runApp（debugPrint 仍捕获）。
• Release version-consistency check (tool/check_release.dart + test/version_consistency_test.dart) plus a CI step; InspectorVersion.value and all version strings bumped to 1.12.0. / 发版版本一致性自检（tool/check_release.dart + 测试）与 CI 步骤；InspectorVersion.value 及各版本串升至 1.12.0。
• Fix timeline card paint crash (non-uniform border with borderRadius); the kind accent is now an inner bar. / 修复时间线卡片圆角 + 异色边框的绘制崩溃，kind 色条改为卡片内竖条。

Context / 背景

The panels were siloed across data sources, real stalls produced zero frames (so FPS read idle), and the "Zone mismatch" assertion was the most common first-run crash for newcomers. A recurring version-drift mistake also motivated an automated guard. / 各面板数据源彼此割裂，真实卡死时零帧导致 FPS 显示空闲，而 "Zone mismatch" 断言是新手最常见的首跑崩溃；反复出现的版本漂移也催生了自动化校验。

Checklist / 检查项

• Title follows Conventional Commits / 标题符合约定式提交
• CI checks pass after merge / 合入后 CI 通过

Test plan

• flutter test is green (283+ tests, incl. new timeline / watchdog / version tests) / flutter test 全绿（含新增时间线 / 看门狗 / 版本测试）
• Build and open the inspector on a device: verify the Timeline tab renders between Routes and Widgets, and toggle the blocking watchdog in the FPS tab / 在设备构建并打开检查器，确认 Timeline 位于 Routes 与 Widgets 之间，并在 FPS 页开关看门狗

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