chore(_example): run multiple docker executors configured from _example/.env

[Scra3]

What

Adds a one-command way to run the agent + the 2 docker executors (behind the nginx gateway on :3400), with all config coming from packages/_example/.env — nothing to edit in the executor example.

New scripts (in packages/_example):

• start:with-executor:multiple-instance — agent + docker executors (reuses the pre-built image)
• start:with-executor:multiple-instance:build — same, rebuilding the executor image

How

• A small wrapper packages/_example/scripts/start-docker-executors.sh sources _example/.env, translates host-local URLs (localhost / 127.0.0.1 / *.development.forestadmin.com) so the containers can reach the host, waits for the agent, then delegates.
• The executor example's executors / executors:build scripts stay config-agnostic (pure docker compose up). Run standalone from the executor example dir, they use that package's own env — not _example/.env.

Fixes to the existing compose

• build.context ../.. → ../../.. so the Dockerfile's COPY . . sees the repo root (was failing with lstat .../packages/packages).
• Map *.development.forestadmin.com dev domains to the host via extra_hosts (they resolve to 127.0.0.1 on the host; inert for prod api.forestadmin.com), so containers can reach a local orchestrator.
• Drop the separate .env.executors flow from the docs/header (config now lives only in _example/.env).

🤖 Generated with Claude Code

Note

Run multiple docker executors configured from _example/.env

• Adds a start-docker-executors.sh script that sources packages/_example/.env, rewrites localhost/127.0.0.1 endpoints to host.docker.internal, and waits for the agent to be reachable before starting executors.
• Adds start:with-executor:multiple-instance and start:with-executor:multiple-instance:build scripts to packages/_example/package.json that run the agent and docker executors concurrently via concurrently --kill-others.
• Updates docker-compose.executors.yml to add extra_hosts entries mapping Forest local-dev domains to host-gateway, and changes the executor-1 build context from ../.. to ../../.. (repo root).
• Risk: the broader Docker build context for executor-1 may include unintended files from the repo root in the image.

^{Macroscope summarized 47612a6.}

[qltysh]

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