Add debug logging to rake-ui

[nicholaspufal]

JIRA link: https://doximity.atlassian.net/browse/CSVUEAN-2825

What is this?

• rake-ui runs rake tasks asynchronously, but today there is very little structured host-app logging around that lifecycle. When a task appears to hang, exits before producing useful output, or never reaches the local task log, maintainers have to infer where execution stopped: request handling, log creation, process handoff, or completion marker writing. That makes failures harder to diagnose than they need to be.

• This adds debug-level lifecycle breadcrumbs with a small, stable, public-safe shape. Each event identifies the rake-ui component, the lifecycle event, the host Rails app name, the rake task name, and the task log id when one exists. It intentionally does not log command strings, argument values, environment values, authentication data, or application-specific metadata.

• I also documented the events and fields in the README so host applications can enable Rails debug logging and know what each breadcrumb means.

Diagram

The lifecycle has a few handoff points, so this is useful context for what the breadcrumbs cover:

sequenceDiagram
    participant Host as Host Rails app
    participant RakeUi as rake-ui
    participant Log as Local task log
    participant Child as Forked task process

    Host->>RakeUi: Execute rake task
    RakeUi-->>RakeUi: debug: task_execution.requested
    RakeUi->>Log: Create task log file
    RakeUi-->>RakeUi: debug: task_log.created
    RakeUi->>Child: Fork execution
    RakeUi-->>RakeUi: debug: task_execution.forked
    Child->>Log: Write command output
    Child->>Log: Write finished marker
    Child-->>RakeUi: debug: task_execution.finished_marker_written

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