healthchecks
Fix ENV instructions to expand $VAR references at set time using the
current env state, preventing self-referencing values like
PATH=/opt/venv/bin:$PATH from producing recursive expansions. Remove
expandEnv from shellPrefix to avoid double expansion.
Fetch sandbox environment variables via `env` before recipe execution
so ENV steps resolve against actual runtime values from the base
template image.
Replace hardcoded healthcheck timing with a Dockerfile-like flag parser
supporting --interval, --timeout, --start-period, and --retries. Add
start-period grace window and bounded retry counting to
waitForHealthcheck.
Add python-interpreter-v0-beta recipe and healthcheck files.
- skip_pre_post flag on builds bypasses apt update/clean pre/post steps for
faster iteration when the recipe handles its own environment setup
- POST /v1/admin/builds/{id}/cancel endpoint marks an in-progress build as
cancelled; UpdateBuildStatus now also sets completed_at for 'cancelled'
- internal/recipe: typed recipe parser and executor (RUN/ENV/COPY steps)
replacing the raw string slice approach in the build worker
- pre/post build commands prefixed with RUN to match recipe step format
