Improve Worktrunk sidebar refresh performance

[nicosuave]

Summary

• gate sidebar onAppear refreshes with a staleness window and trigger-aware rerun behavior
• bound parallel repo/worktree refresh concurrency to avoid large fan-out spikes
• overlap git tracking refresh with session refresh and skip heavy diff scans for clean trees

Verification

• zig build
• zig build test -Dtest-filter=Worktrunk
• zig build run (app launched successfully)

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve rerun when awaiting an already-finished refresh task

If refreshAll(trigger:) is called in the small window after the internal task has finished but before refreshAllTask is cleared, this branch still takes existing, sets refreshAllNeedsRerun = true, awaits an already-completed task, and returns without starting a new refresh. In that scenario, .repositoryAdded, .worktrunkInstalled, or .manual requests can be dropped, leaving sidebar/worktree state stale until some later refresh happens.

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