Closes the gap the user hit running `pnpm work decompose --execute`:
sandcastle errored with `Image 'sandcastle:template-vertical' not
found locally. Build it first with 'sandcastle docker build-image'`,
but neither the README nor the runbook documented this step.
README.md: new "Sandcastle setup (one-time)" section after Quick
reference. Three commands (docker info, build-image, auth) — the
minimum needed to make dispatch work. Links to the runbook for the
full lifecycle.
docs/guides/runbook.md: Prerequisites in "Using Sandcastle" grow
from 4 to 5 items. New step 2 walks through `sandcastle docker
build-image`, quotes the exact "Image not found locally" error so
agents searching for the string land on the fix, and shows the
remove-image + rebuild flow for Dockerfile edits.
.sandcastle/README.md: new "Build the sandbox image (one-time)"
section parallel to the env section, cross-linking to the runbook.
scripts/work/decompose.mjs + scripts/work/dispatch.mjs: when the
sandcastle error message matches the "Image '.+' not found locally"
pattern, the dispatcher now prints the build-image command inline
above the generic "See runbook" line. The error stack itself remains
unchanged.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Captures the decision to adopt @ai-hero/sandcastle as the orchestration
substrate for agent-driven development in this template. Records the
8-point decision (workspace dep, .sandcastle/ prompts, Dockerfile,
dispatch.mjs orchestrator, planning vs execute modes, generator-first
reviewer check, bring-your-own-key, per-task max-attempts), the four
alternatives considered (bare CLI / Copilot Workspace / custom-from-
scratch / no orchestrator), and four trade-offs (external dep, token
cost, Docker dependency, manual state mutation in v1).
Surfaces the decision at the top of README.md and AGENTS.md so new
contributors see the agent-driven framing before they hit the package
map or daily commands.
