Add SPM build tool plugin for embedding ID discovery

[t-jimbo]

Summary

• Adds NubrickDevTool SPM build tool plugin that scans host app Swift source files at build time for NubrickSDK.embedding("...") / embeddingUIView("...") calls
• Extracts string literal IDs and generates a @_cdecl symbol compiled into the app binary
• At SDK init (debug builds only), discovers the IDs via dlsym and reports them to the track server as an embedding_discovery event
• Zero changes to existing public API — developers only add the plugin to their target

How it works

1. Build time: Plugin scans .swift files → extracts embedding IDs → generates NubrickEmbeddingIds.generated.swift
2. Runtime: NubrickSDK.initialize() → dlsym("_nubrick_embedding_ids") → sends IDs to track server

Consumer integration

// In Package.swift target:
plugins: [.plugin(name: "NubrickDevTool", package: "Nubrick")]

Or in Xcode: Target → Build Phases → + → Run Build Tool Plug-in → NubrickDevTool

Server-side contract

• New TrackEvent.typename: "embedding_discovery"
• New field: embeddingIds: [String]
• Recommended: upsert per (projectId, appId, appVersion)

Limitations

• Only captures static string literals (dynamic IDs are missed by design)
• Plugin must be applied to one target per final binary
• Debug-only reporting (#if DEBUG)

Test plan

• swift build --target NubrickDevToolRunner passes
• Plugin generates correct file when applied to Example-Local
• Runtime reports IDs on initialize (verify via breakpoint/proxy)
• No-op when plugin is not applied

🤖 Generated with Claude Code