fix: task_manager close action supports archiving done tasks (#359)

[MatthewSuttles]

Summary

• close action now archives tasks already in done status instead of returning an error — agents can archive any task regardless of its current status
• New close_all action bulk-archives all non-archived done tasks, with optional assigned_to filter
• Tool schema updated to expose close_all in the action enum
• Specs updated: replaced the already done = error expectation with correct archive behavior, full coverage added for close_all

Root cause

close_task called TransitionService with new_status: "done". TransitionService rejects the call when the task is already in that status ("Task is already 'done'"). The Task#archive! method existed but was never wired up in the executor.

Changes

• app/services/tools/task_manager_executor.rb — close_task detects done status and calls archive!; new close_all_tasks method for bulk archival
• db/seeds/tools.rb — close_all added to the action enum
• spec/services/tools/task_manager_executor_spec.rb — updated + new specs

Test plan

• close on a non-done task: transitions to done as before
• close on a done task: archives it, returns success
• close on an already-archived task: returns failure
• close_all with done tasks: archives all non-archived done tasks
• close_all with no done tasks: returns informational message
• close_all with assigned_to filter: only archives that agent's done tasks