feat(jobs): expand environment variables in paths

examples/jobs/README.md

@@ -0,0 +1,80 @@
+# RelSpec job examples
+
+Run these commands from this directory:
+
+```bash
+cd examples/jobs
+
+# List every job from relspec.yml and the additional relspec.*.yml files.
+relspec job list
+
+# Validate a job and print its resolved plan without reading or writing data.
+relspec job run build-schema --plan
+
+# Build PostgreSQL DDL from the two DBML inputs.
+relspec job run build-schema
+
+# Run a job's dependency chain. This runs build-schema first, then build-json.
+relspec job run build-json
+
+# Inspect build-json's output. The from_job input adds the dependency automatically.
+relspec job run lint-schema
+
+# Extract only the posts table.
+relspec job run posts-only
+
+# List migration scripts in deterministic order without connecting to a database.
+relspec job run migration-order
+
+# Render one TypeScript file per table using the example template.
+relspec job run generate-typescript
+
+# Compare the two example schemas and write the summary to the logfile.
+relspec job run compare-schemas
+
+# Use an environment variable in an output path.
+export VST=build/typescript
+relspec job run generate-typescript --plan
+relspec job run generate-typescript
+```
+
+Database jobs use environment variables for connection strings. Set them in
+the shell before running the jobs; do not put connection strings in YAML:
+
+```bash
+export SOURCE_DB_URL='postgres://user:password@localhost/source_db'
+export TARGET_DB_URL='postgres://user:password@localhost/target_db'
+
+# Read the source database and write a local DBML snapshot.
+relspec job run snapshot-database
+
+# Preview migration execution without connecting to PostgreSQL.
+relspec job run apply-migrations --plan
+
+# Execute the migrations against TARGET_DB_URL.
+relspec job run apply-migrations
+```
+
+The `apply-migrations` job demonstrates execution from multiple directories:
+
+```yaml
+script_dirs:
+  - migrations/core
+  - migrations/tenant
+output:
+  format: pgsql
+  conn_env: TARGET_DB_URL
+```
+
+RelSpec combines the SQL files from both folders in deterministic order before
+executing them against the configured PostgreSQL database.
+
+To use a different directory or manifest, pass `--dir` or `--file`:
+
+```bash
+relspec job list --dir /path/to/project
+relspec job run build-schema --file /path/to/project/relspec.yml --plan
+```
+
+See [../../docs/JOB_FILES.md](../../docs/JOB_FILES.md) for the complete job
+file reference.