refactor(cli): extract todo completion owner

[songoow]

Summary

• loopx/cli_commands/todo.py reached 1185 lines, above the 1098-line frozen budget in examples/cli-command-module-size-ownership-command-modularization-smoke.py, which is one of the shard-0 failures keeping Full Public Smokes red on main. Follow the smoke's own instruction and the turn_dsh_host.py precedent (fix(ci): repair public smoke regressions #3856): extract one cohesive command owner instead of raising the budget.
• Move the loopx todo complete owner into loopx/cli_commands/todo_complete.py: the settlement-requirement and settlement-error rules, the turn-scoped settlement gate plus complete_goal_todo write (run_todo_complete), and the post-commit settlement readback and post-writeback hook dispatch (finalize_committed_todo_completion, TodoCompletionOutcome). handle_todo_command keeps subcommand dispatch, rollout-event append, and the runtime-shadow mirror, then hands the outcome to the finalizer, preserving the original ordering and payload mutation.
• Moved code is mechanically identical apart from two helpers losing their private underscore (they are now the owner module's API) and the inline project/state-file expansion using the existing path_args mapping. No compatibility wrapper: the only importers were two tests, re-pointed to the new owner.
• todo.py drops to 972 lines, inside the 1000-line default, so the frozen "todo.py": 1098 entry is retired (a tightening, not a raise). No CLI flags, outputs, or defaults change.
• Disclosure of a remaining baseline failure: on current main the same smoke also fails on turn.py, which reached 1047 lines in fix(coordination): route the legacy todo write transaction through the effective runtime root #3904 with no frozen entry. This PR does not touch turn.py; whether to pin it or extract another owner is a maintainer decision.

Companion baseline PRs for the other shard failures: #3942 (goal configuration catalog smoke) and #3943 (concise help and manpage parity). Each is independent and can merge in any order.

Issue Or Task

• Closes #
• Contributor task ID: baseline repair for the red Full Public Smokes workflow on main (shard 0)

Validation

• python3 -m py_compile loopx/cli_commands/todo.py loopx/cli_commands/todo_complete.py
• python3 examples/cli-command-module-size-ownership-command-modularization-smoke.py -> todo.py budget satisfied; the only remaining assertion failure is the pre-existing turn.py 1047 > 1000 from fix(coordination): route the legacy todo write transaction through the effective runtime root #3904
• characterization set green before and after the move: tests/test_cli_argument_diagnostics.py, tests/control_plane/test_quota_settlement.py, tests/control_plane/test_coordination_runtime_shadow_adapter.py, tests/test_cli_entrypoint.py, tests/test_goal_mode_mcp_completion_validation.py -> 174 passed
• heartbeat-quota-flow, monitor-poll-writeback, task-lease-runtime, multi-agent-role-successor-todos, cli-control-plane-command-modularization smokes -> ok
• python3 -m pytest tests -q -k "todo or cli or help" -> 1132 passed
• loopx canary premerge --from-git-diff --git-diff-base <official main> -> 18/18 selected checks passed, 0 manual holds
• git diff --check clean; commit carries the DCO trailer

Type of Change

• Refactoring (no functional changes)

LoopX Area

• Control plane (goals, todos, quota, scheduler, registry, runtime)

Technical Direction

• Core control-plane hardening

• Target base branch: main

• Direction tracker or promotion unit: Full Public Smokes baseline

Boundary Checklist

• I did not commit .loopx/, .codex/goals/, live ACTIVE_GOAL_STATE.md, credentials, private benchmark traces, verifier output, raw agent sessions, internal document links, or local machine paths.
• I did not duplicate maintainer-owned benchmark work unless a maintainer split out a public issue for it.
• I kept the change scoped to the linked issue/task.
• Every commit includes a DCO Signed-off-by trailer (git commit -s).

[songoow]

Closing to keep the review queue small. With turn.py also above the default budget after #3904, the module-size smoke stays red on main regardless of this extraction, so the pin-versus-extract decision belongs to maintainers first. The extraction is validated and stays available on codex/cli-todo-complete-owner (todo.py 1185 -> 972 lines, no behavior change) if that is the preferred path.