Generalize the terminal history demo

Traceability

• Spec ID: terminal-history-demo
• Status: Implemented

Intent

Make the terminal history animation a project-neutral Better Harness development tool. It should discover current report roots for one workspace or read explicitly supplied host-specific roots without mixing unrelated projects.

Acceptance Scenarios

• AC-1: The primary entrypoint and documentation use the Better Harness name; no pre-public compatibility wrapper remains.
• AC-2: With --workspace <project>, or the current working directory by default, discovery reads existing .qoder/better-harness and .codex/better-harness report roots. It may recognize the same product directory names below another first-level hidden host directory.
• AC-3: Repeated --history-root <path> arguments bypass workspace discovery, expand ~, and may point directly at paths such as ~/.qoder/better-harness or ~/.xx/better-harness. Missing roots produce a concise diagnostic that names the attempted scope.
• AC-4: When multiple current host roots exist for one workspace, their valid findings.json runs form one chronological history with duplicate file paths removed. Report-contract boundaries remain visible and source artifacts are never rewritten.