Stream embedded ZIP entries directly into the parser

[drauf]

Problem

Embedded ZIP import still creates a complete File for every selected ZIP entry before parsing starts.

For large support ZIPs, this creates avoidable memory pressure:

• fflate collects decompressed chunks for an entry
• Watson combines them into a File
• the parser later reads that File again through readFileLines
• all selected files can exist before parsing completes

The current incremental import work reduces base64 lifetime and starts parser work earlier, but it still materializes each selected entry as a File.

Goal

Allow embedded ZIP entry content to flow directly into the parser in bounded chunks.

Keep manual drag-and-drop upload support unchanged for users.

Scope

• Define a source-agnostic parser input contract:
  • entry name
  • entry size when known
  • async byte or line stream
• Keep File as the browser upload boundary type
• Adapt manual uploads from File.stream() to the shared parser input contract
• Adapt fflate ZIP entry chunks to the same contract
• Update readFileLines and the worker protocol to consume streamed entry content
• Preserve parser ordering between thread dumps and CPU usage files
• Apply backpressure so ZIP extraction does not outrun parser consumption
• Release entry buffers once parsing of that entry completes
• Keep unknown file totals explicit in progress reporting

Out of scope

• Supporting additional archive formats
• Changing the manual upload UI
• Replacing the existing parser or thread-dump model
• Adding a new benchmark framework

Success criteria

• Embedded ZIP import does not create a File for every selected entry
• Memory use remains bounded while parsing large embedded archives
• Manual uploads continue to work through the shared input contract
• Thread-dump and CPU usage pairing remains correct
• Invalid ZIP input and parser errors remain user-visible
• Add unit tests for streamed entry boundaries and worker backpressure
• Compare manual-upload and embedded-import timing before and after the change