Fix VS Code workspace discovery and code activation - #592

Summary

• Discover nested dw.json files in parent-folder and multi-root VS Code workspaces, preferring workspace order and the shallowest project configuration.
• Allow nested project folders such as sfra/ to be pinned as the B2C Commerce root from Explorer and document all supported CLI configuration sources.
• Treat activation of an already-active code version as an idempotent success across the SDK, CLI, and VS Code extension. Preserve actual OCAPI fault details and hide redundant activation choices when the active version is known.

Testing

• pnpm --filter @salesforce/b2c-tooling-sdk run test:agent (2,045 passing, 7 pending)
• pnpm --filter @salesforce/b2c-cli run test:agent (1,425 passing)
• pnpm --filter b2c-vs-extension run test (full workspace-shape and activation matrix)
• pnpm run lint:agent
• pnpm run typecheck:agent
• pnpm run docs:build
• Built and inspected b2c-vs-extension-1.0.2.vsix

Dependencies

• No net-new third-party dependencies were added
• If net-new third-party dependencies were added, rationale/discussion is included and 3pl-approved is set by a maintainer

• Relevant package tests pass
• Code is formatted and lint passes