Discover project commands/skills from additional working directories (--add-dir)

Problem

Claude Code only scans the primary CWD's .claude/commands/ and .claude/skills/ for slash commands and skills. Any .claude/ directory inside a path added via --add-dir (or the IDE extension's "additional working directories") is ignored.

Repro

1. Launch Claude Code with primary CWD = projectA, and projectB added as an additional working directory.
2. projectB/.claude/commands/foo.md exists and is valid.
3. /foo does not appear in the slash-command list and cannot be invoked.

Expected

/foo is discovered and available, optionally namespaced (e.g. /projectB:foo) to avoid collisions across added directories.

Why this matters

Multi-repo workspaces are common — e.g. a backend repo plus a separate frontend repo that together make up one product. Today the only workarounds are all bad:

• Relaunch with a different primary CWD (loses context on the other repo).
• Duplicate commands into ~/.claude/ (loses per-project versioning and git-sync across machines).
• Copy the command file into the primary project (lives in the wrong repo, drifts from its source).

If a directory was intentionally added to the workspace, its project-scoped commands/skills should come with it.

Environment

• Claude Code VSCode extension on Windows 11
• Model: Opus 4.7