fix: resolve ${VAR} templates against environment variables

[JoshuaLelon]

Summary

resolveArgsTemplate() only looked up ${VAR} from workflow args (passed via --args-json), so env: { MY_VAR: "${MY_VAR}" } in workflow YAML produced the literal string "${MY_VAR}" instead of the actual value from process.env. This also affected ${VAR} in command, stdin, and cwd fields.

The fix threads the accumulated environment through resolveTemplate, resolveStdin, and resolveCwd so ${VAR} falls back to the process/workflow environment when not found in args. Args still take precedence over env vars.

Also adds relative cwd resolution — cwd: ./scripts now resolves relative to the workflow file's directory instead of being passed as-is to spawn().

lobster-biscuit

Repro Steps

1. Create a workflow file with env: { TEST_VAR: "${TEST_VAR}" }
2. Run TEST_VAR=hello lobster run --file workflow.lobster
3. The step's process.env.TEST_VAR is the literal "${TEST_VAR}" instead of "hello"

Root Cause

resolveArgsTemplate only checked args (workflow-defined args from --args-json). It had no fallback to the environment, so any ${VAR} not defined in args was returned verbatim.

Behavior Changes

• ${VAR} in env, command, stdin, and cwd values now resolves from the environment when not found in workflow args
• Precedence: args > env > literal (unchanged match kept as-is)
• Relative cwd values (e.g. ./scripts) now resolve relative to the workflow file directory
• No breaking changes to existing behavior — unresolved ${VAR} still pass through as before

Tests

6 new tests in test/workflow_env.test.ts:

Test	Result
env var substitution resolves from process.env	✅
workflow-level env overrides parent env	✅
step-level env overrides workflow-level env	✅
args take precedence over env in template substitution	✅
env vars resolve in command templates	✅
relative cwd resolves from workflow file directory	✅

All 53 tests pass (47 existing + 6 new).

pnpm build && pnpm test — clean.

Manual Testing

$ TEST_VAR=hello node bin/lobster.js run --file test/fixtures/env-test.lobster
["hello"]

Sign-Off

• Models used: Claude Opus 4.6
• Submitter effort: planned + reviewed
• Agent notes: ~25 lines of source changes; all optional env params preserve backward compatibility