🤖 fix: make compaction control-plane and atomic

[ammar-agent]

What

• Adds a dedicated control-plane endpoint workspace.compactHistory to trigger compaction (instead of inserting /compact as user text).
• Tracks compaction via session state (activeCompactionOperation), removing legacy history-scanning detection.
• Hardens history replacement so it only happens on successful stream-end with a validated summary.
• Replaces compaction history atomically via HistoryService.replaceHistory() (avoids “delete then crash” window).

Why

Auto-inserted /compact could be sent/queued as plain text and treated like a normal message. This makes compaction deterministic and removes ambiguity between UI display and backend execution.

Notes

• Summary validation currently requires non-empty text with a minimum word threshold to avoid replacing history with truncated output.
• Frontend force-compaction and idle-compaction are migrated to the new endpoint.

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Generated with mux • Model: openai:gpt-5.2 • Thinking: high

[chatgpt-codex-connector]

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