Remove direct state.py imports — route through Gremlin instances

[xbrianh]

Finding

Eighteen non-test files import directly from gremlins.executor.state without going through a Gremlin instance. This creates a second access path to state that bypasses whatever invariants Gremlin is meant to enforce.

Stages — drop State import, pass Gremlin explicitly

All stage files import State for their run(state) signature, but stages already hold a .gremlin attribute set via _set_gremlin_recursive. The magic assignment should be replaced by passing gremlin explicitly: Stage.run(gremlin) -> Outcome.

Stages don't mutate state — they produce artifacts and return an Outcome. The gremlin manages all state transitions (recording attempts, advancing scope, persisting to disk). Stages are pure-ish workers: given a gremlin for context, produce outputs. State becomes fully internal to Gremlin; stages never see it.

File	Currently imports
gremlins/stages/base.py	State
gremlins/stages/composite.py	State
gremlins/stages/exec.py	State
gremlins/stages/loop.py	State
gremlins/stages/parallel.py	State, StateData
gremlins/stages/sequence.py	State
gremlins/stages/agent.py	State
gremlins/stages/agent_runner.py	State
gremlins/utils/proc.py	State (TYPE_CHECKING only)

Design: State as an attribute of Gremlin

State becomes gremlin.state, owned and managed by Gremlin. The runner calls stage.run(gremlin); stages read what they need from the gremlin (client, artifact_dir, repo, instructions, etc.) and return an Outcome.

Per-stage client overrides are handled in _collect_stages, which already iterates stages and resolves e.client or PACKAGE_DEFAULT. The resolved client (and stage_model) is patched onto gremlin.state inside the make_runner closure before calling stage.run(gremlin), keeping the override local to that stage's execution. Stages never see it directly.

Other callers — route through Gremlin

These files call build_state, resolve_artifact_dir, landable_shape, validate_gremlin_id, etc. directly. They should receive or construct a Gremlin and use its interface instead.

File	Currently imports
gremlins/run_child.py	State, StateData, build_state, validate_gremlin_id
gremlins/spawn/child.py	State, StateData, build_state, validate_gremlin_id
gremlins/spawn/pipeline.py	StateData, validate_gremlin_id
gremlins/fleet/land.py	landable_shape, resolve_artifact_dir, StateData, build_state
gremlins/fleet/views.py	StateData
gremlins/executor/parallel_state.py	StateData, resolve_state_file
gremlins/executor/run.py	StateData, resolve_artifact_dir, resolve_state_file
gremlins/launcher.py	StateData, validate_gremlin_id
gremlins/cli/resume.py	validate_gremlin_id

Goal

gremlins.executor.state becomes an internal implementation detail of Gremlin. External callers hold Gremlin instances; stages take a gremlin argument and return an Outcome.