MCP Server: Fix embedded mode (CoreEmbedded.Supervisor missing)

[decebal]

Problem

The ghcr.io/all-source-os/allsource-mcp-server:latest Docker image supports CORE_MODE=embedded in its runtime.exs config, but the referenced module McpServerElixir.Infrastructure.CoreEmbedded.Supervisor doesn't exist in the release, causing immediate crash on startup:

(ArgumentError) The module McpServerElixir.Infrastructure.CoreEmbedded.Supervisor was given as a child to a supervisor but it does not exist

Expected behavior

Running with CORE_MODE=embedded and CORE_DATA_DIR=/data should start an in-process AllSource store that reads directly from WAL + Parquet files, enabling MCP tool queries without a separate Core container.

Use case

Claude Code MCP integration for local debugging — point the MCP server at a Tauri app's embedded AllSource data directory to query events, snapshots, and entity state without running the full Core stack.

Steps to reproduce

docker run --rm --platform linux/amd64 \
  -v "/path/to/allsource/data:/data:ro" \
  -e CORE_MODE=embedded \
  -e CORE_DATA_DIR=/data \
  ghcr.io/all-source-os/allsource-mcp-server:latest

Environment

• Image: ghcr.io/all-source-os/allsource-mcp-server:latest (tag 0.14.8)
• Platform: macOS (Apple Silicon, using --platform linux/amd64)