Feature: Pause and Resume Scan Functionality

[techmore]

Summary

Add true pause-and-resume support for long-running scan jobs.

The current runtime already supports starting jobs, reporting status, and cancelling running scan/report work. What is missing is a resumable execution model that can stop work intentionally without discarding useful progress.

Current State

• scan and report jobs have active job-state tracking
• cancellation exists
• the UI already exposes pause/resume affordances, but there is no real resumable backend workflow behind them

Remaining Problem

Today, interrupting a long-running scan effectively means cancellation. Users cannot pause work and later continue from a stable checkpoint.

For large networks or long report-generation flows, that means:

• partial progress is lost
• long operations must restart from the beginning
• the existing UI controls are more suggestive than real

Proposed Scope

1. Execution Model

• define what can realistically be paused and resumed
• distinguish between quick scan, deep scan, chunked report scan, and PDF-only tasks
• prefer resumable checkpoints at safe workflow boundaries instead of pretending every subprocess can be suspended transparently

2. State Persistence

• store enough progress to resume meaningfully
• preserve discovered results and remaining work units where practical
• avoid duplicate scanning when resuming from chunked or multi-target work

3. UI Behavior

• make pause/resume controls reflect actual backend capability
• show whether a job is pausable, paused, resuming, or only cancellable

Implementation Notes

Likely touch points in the current architecture:

• job registry and job-status events
• scan/report workflow orchestration
• frontend job controls and status rendering

This should be designed around checkpointed workflow resumption, not around attempting to suspend arbitrary nmap subprocesses mid-packet.