Error codes

Every structured failure uses an ECP_* code. --json prints it on the error envelope: { ok: false, error: { code, message, path, suggestions } }. Source of truth in the monorepo: packages/core/src/types/errors.ts.

Code	When
`ECP_WORKFLOW_LOAD`	The workflow file could not be loaded or compiled
`ECP_PLUGINS_MISSING`	A required plugin (or `--format` plugin) is not installed
`ECP_CAPABILITY_UNKNOWN`	A step id is not in the registry
`ECP_INPUT_INVALID`	Step input failed schema validation (wrong `ref()`, bad payload)
`ECP_REF_UNRESOLVED`	A `ref()` target does not exist
`ECP_BINDING_INVALID`	An extension or policy binding is malformed
`ECP_ENVIRONMENT_UNSUPPORTED`	A definition’s `.supports()` excludes this host
`ECP_SECRET_MISSING`	`secrets("key")` has no resolved value
`ECP_POLICY_DENIED`	A policy rejected the step
`ECP_RUN_PAUSED`	The run is waiting (for example approval). Resume with `ecp runs resume`
`ECP_STEP_FAILED`	The capability threw or returned a failure
`ECP_OUTPUT_INVALID`	Step output failed schema validation
`ECP_PLUGIN_DENIED`	You declined a third-party plugin install
`ECP_RERUN_INCOMPATIBLE`	`runs rerun --from` cannot apply because the graph changed

Process exits: 0 success, 1 failed run, 2 usage, 3 validation, 4 plugin/environment load.

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