Implement \`toggleWatchSignal(id)\` in \`signal_debug.ts\` to enable toggling reactive watch listeners on individual signal graph nodes.
- Create reactive \`Watch\` instances using \`createWatch\` to log signal value/state changes to the console when active.
- Use \`WeakRef\` mapping and \`FinalizationRegistry\` (\`watchCleanupRegistry\`) so active watches do not retain strong references to signal nodes or prevent garbage collection.
- Expose \`watched\` status on \`DebugSignalGraphNode\` and publish \`toggleWatchSignal\` onto \`window.ng\` in development mode.
- Add acceptance tests covering watch activation, signal mutation logging, manual disposal, GC cleanup, and safe invalid ID handling.
Move the DebugSignalGraph, DebugSignalGraphEdge, and DebugSignalGraphNode interfaces from packages/core/src/render3/util/signal_debug.ts into the packages/core/primitives/devtools/src package. This decouples the signal graph debug types from runtime render3 utilities and allows devtools and internal core tooling to import them directly from primitives as type-only exports.
Extract the AI tool definition interfaces from the core debug module to the devtools primitives module. This relocates ToolDefinition, ToolGroup, and DevtoolsToolDiscoveryEvent to the primitives folder, exposing them cleanly via "export type" in the devtools entry point, improving module organization and readability.
Cameron Smick