The exposed binary, `Sandcastle:` error prefix, and on-disk
`.sandcastle/` working directory were all called `sandcastle`,
which collides with @ai-hero/sandcastle — this package's own
direct dependency. Disambiguate by renaming every reference to
our wrapper to `sandcastle-drain`, while leaving references to
Pocock's library (the @ai-hero/sandcastle dependency, sandcastle.run()
calls, the `sandcastle` GitHub label, comments describing library
behavior) intact.

Touches the bin field, error/log prefixes, `.sandcastle/` →
`.sandcastle-drain/` everywhere (including the prompt templates
the agents read inside the sandbox), prompt templates, principle
docs, agent-docs, the ADR, README, package.json description, and
CONTEXT.md.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>