Proposal: Add support for Build debugging

Problem

It can be a struggle to understand what happens during a Docker build. They lack visibility into how the build context is used, what layers are created or cached, and how the filesystem changes step-by-step, making it difficult to diagnose slow or broken builds.

• How the build context is prepared.
• How layers are created, reused, or invalidated.
• How the filesystem changes between layers.
• Whether cache hits or misses occur, and why.

Proposed Solution

Enhance the Docker DX extension to surface more detailed build debugging information, ideally integrated into the VS Code UI:

• Show how the build context is assembled (files included/excluded).
• Visualize each build layer: what files were added, modified, or deleted.
• Indicate cache hits/misses clearly at each build step.
• Expose the current working directory (WORKDIR) and filesystem state before and after a step.
• Provide build step logs with additional debugging output (optionally toggled on).

This could be surfaced through:

• A side panel view summarizing build steps and cache usage.
• Inline diagnostics in Dockerfile editors (e.g., “this line caused a cache miss”).
• Enhanced logging in the VS Code Terminal output.

Start by examining the Docker DX extension’s current build experience in the VS Code UI, including Dockerfile editor diagnostics and VS Code Terminal output. Define a narrower first milestone around build context, layer changes, cache status, WORKDIR state, or enhanced logs; completion should specify which debugging information is surfaced and where.