feat(electron): add agent heartbeat pulse light

[cjvayhxy-dev]

Summary

• add an Agent heartbeat pulse light for header and expanded sidebar rows
• extend shared session indicator status with error and red error rendering in sidebar/tab indicators
• show compact hover progress for current phase, Task progress, delegated child-session progress, retry/error/blocked states, and tool fallback
• scope delegated child progress to the current running turn to avoid historical child sessions polluting hover progress

Validation

• bun install
• bun test apps/electron/src/renderer/atoms/agent-atoms.test.ts
• bun test apps/electron/src/renderer/components/agent/AgentStatusPulseLight.test.ts
• bun test apps/electron/src/renderer/components/agent/task-progress.test.ts
• bun test apps/electron/src/renderer
• bun run typecheck
• bun run --filter='@proma/electron' build:renderer
• git diff --check