Implement set_tasks_completion lifecycle flow

[deverman]

Summary:

• implement set_tasks_completion in the shared mutation pipeline from Implement update_tasks for Homogeneous Bulk Field Patches #30
• expose the lifecycle operation through CLI and MCP
• use documented Omni Automation task lifecycle APIs markComplete and markIncomplete

Validation:

• node --check Plugin/FocusRelayBridge.omnijs/Resources/BridgeLibrary.js
• swift test
• ./scripts/install-plugin.sh
• swift run focusrelay bridge-health-check
• swift run focusrelay get-task e-Wn5k27h6g --fields id,name,completed,completionDate
• swift run focusrelay set-tasks-completion e-Wn5k27h6g --state completed --verify --return-fields id,name,completed,completionDate
• swift run focusrelay set-tasks-completion e-Wn5k27h6g --state active --verify --return-fields id,name,completed,completionDate

Notes:

• this PR is intentionally stacked on Implement update_tasks mutation flow #41 and should not merge before Implement update_tasks mutation flow #41 lands
• live validation used a non-repeating task and restored it to active state after the test
• repeating-task handling follows the documented markComplete behavior and reports the advanced-occurrence case in the per-item message

[deverman]

Merge-order note: this PR is intentionally stacked on #41 and should not merge before #41 lands. After #41 merges, retarget or rebase this branch onto master before final review and merge.

[deverman]

Merge-order note: the follow-up work for issue #32 is being stacked on top of this PR because task move and reparent behavior reuses the same task mutation surface. Merge #42 before the future #32 PR.

[deverman]

Updated #42 on top of current master after #41 merged, resolved squash-merge conflicts, and retargeted the PR base to master.

Validation:

• node --check Plugin/FocusRelayBridge.omnijs/Resources/BridgeLibrary.js
• swift test (79 tests passed; existing MCP SDK deprecation warnings only)
• git diff --check
• ./scripts/install-plugin.sh; fully restarted OmniFocus
• ./.build/debug/focusrelay bridge-health-check
• ./.build/debug/focusrelay set-tasks-completion --help
• Preview-only live check: ./.build/debug/focusrelay set-tasks-completion ixKfgse5Mw- --state completed --preview-only --verify --return-fields id,name,completed,completionDate
• Real live lifecycle check: completed ixKfgse5Mw- with --verify, then restored it with --state active --verify
• Confirmed restore with ./.build/debug/focusrelay get-task ixKfgse5Mw- --fields id,name,completed,completionDate
• swift run focusrelay benchmark-gate-check --tool task-counts
• swift run focusrelay benchmark-gate-check --tool list-tasks
• swift run focusrelay benchmark-gate-check --tool project-counts

Merge order note: this should merge after #41 and before #43.