Salvage of #14967 by @luyao618 onto current main. Chosen over the parallel #14969 for robustness.

Closes #14944.

What this PR does

Stops the background memory/skill review from re-surfacing stale tool results from the prior conversation as if they just happened. After e.g. creating a cron reminder, subsequent 💾 background-review notifications would include Cron job '<name>' created. again on every run, even though cron wasn't touched.

How

The review agent forks with conversation_history=messages_snapshot, so its _session_messages contains inherited tool messages. The scan that builds the 💾 summary walked the whole list and treated historical tool successes as new review actions.

@luyao618 extracts the scan into a testable AIAgent._summarize_background_review_actions staticmethod that:

• Records every tool_call_id in the snapshot and skips review messages whose tool_call_id matches
• Falls back to content-equality for tool messages that lack a tool_call_id
• Hardens the data.get('success') branch against non-dict JSON payloads (latent bug — bare-string/list content previously raised)

Why this over #14969

#14969 used a slice approach (_session_messages[len(snapshot):]) which is smaller but brittle: if any future init step reorders, filters, or deduplicates the history (compression, prefix-cache replay, future hydration logic), the slice boundary silently drifts and stale results leak through again. ID-based matching is immune. #14967 also matches the issue author's explicit suggested approach verbatim and fixes the non-dict JSON crash.

Validation

• tests/run_agent/test_background_review_summary.py — 8/8 pass (new file)
• Full tests/run_agent/ — 940/940 pass (the 2 other failures are pre-existing on current main, unrelated)
• E2E: reproduced the exact Background review notification includes stale tool results from conversation history #14944 scenario; fix filters stale cron + preserves new review action

Co-authored-by: @luyao618