Implement `set_tasks_completion` for Homogeneous Bulk Completion State

[deverman]

Summary

Implement set_tasks_completion / focusrelay set-tasks-completion for homogeneous bulk task lifecycle changes.

This tool owns complete/uncomplete behavior and keeps lifecycle semantics out of update_tasks.

Scope

Supported v1 states:

• completed
• active

Input:

• a list of task IDs
• one shared target state for all IDs

Out of scope:

• any other task field updates
• moves/reparenting
• mixed per-item states in one request

Public Behavior

• use lifecycle semantics, not a generic writable boolean field
• support previewOnly
• support verify
• default output is compact summary data with optional returnFields

Acceptance Criteria

• completing tasks works for homogeneous bulk input
• uncompleting tasks works for homogeneous bulk input
• repeating-task behavior is verified and reported correctly
• post-write verification matches final task state
• CLI and MCP behavior is identical in structure

Test Plan

• complete task
• uncomplete task
• repeating-task completion behavior
• invalid ID handling
• preview-only behavior
• verify readback behavior

Notes

This issue should use the documented Omni Automation lifecycle functions rather than trying to route completion through update_tasks.

[deverman]

Execution and merge-order note: issue #31 is intentionally stacked on PR #41 because task completion should reuse the update-task public surfaces and mutation plumbing already added there. Merge PR #41 before merging the future PR for this issue.

[deverman]

Implementation is now in draft PR #42. Merge-order reminder: PR #42 remains intentionally stacked on #41 and should be reviewed and merged only after #41 lands.