feat: Add dev toolbar for live diagnostics and actions

[charlesvien]

Problem

Diagnosing incidents today requires shipping hand-patched debug builds with IPC timings (had to do this for the morning incident), developer actions are scattered across the app and the AI has no runtime telemetry to read when debugging user reports.

Changes

1. Add Dev Toolbar mounted in App root with Agents, CPU, Memory, Network, Logs, Health and IPC Timings panels
2. Consolidate dev actions in one place: crash/restart main, reload renderer, open log file, open user-data dir, trigger toast, react-scan toggle, network simulation (offline/slow)
3. Capture electron-log entries, network requests and IPC timings into a ring buffer when dev mode is on, dumped to the on-disk log file so the AI can read it when debugging user reports
4. Add main-process dev services (flags, metrics, network, logs, actions) behind a tRPC dev router with live snapshots and subscriptions
5. Add "Developer mode" toggle in Advanced settings to gate the toolbar and capture, replacing the patched-build workflow
6. Add platform IAppMetrics abstraction with an Electron adapter

How did you test this?

Manually

Publish to changelog?

no

[charlesvien]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat: Add dev toolbar for live diagnostics and actions #2276 👈 (View in Graphite)
• refactor: The Plan #2275
• main

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