Slice 0: Tooling skeleton — file-based entry + ToolApp + Tools.Tests #1

Slice 0 of the SDK build-out (vertical slices; the map is canonical for scope and sequencing).

• Map: docs/superpowers/plans/2026-08-10-implementation-slice-map.md — § Slice 0
• Detail plan: docs/superpowers/plans/2026-08-10-slice-00-tooling-skeleton.md — its task checkboxes are the canonical task-level progress
• Deviation protocol: docs/agents/deviation-protocol.md
• Branch: feature/slice-00-tooling-skeleton (worktree; one PR to master; merge closes this issue)

Done definition: the map's "Done definition — every slice".