[Bug] Subagent per-call model overrides not preserved on session resume; /status displays session model instead of actual subagent model

Bug Description

▎ Subagent per-call model override is dropped on session resume; /status shows session model for subagents
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▎ 1. Session on Fable 5, /effort ultracode (session-only) set at session start.
▎ 2. Four subagents launched via the Agent tool with explicit model: "sonnet". Transcripts confirm they ran on claude-sonnet-5 (14:25:05–14:25:23 UTC).
▎ 3. At 14:25:41 UTC the session was re-instantiated under a new session ID (new session/tasks dir created; session-only ultracode was dropped at the same time).
▎ 4. From 14:26:02 UTC all four in-flight subagents continued on claude-fable-5 — the per-call override stopped applying after the resume.
▎ 5. A fifth subagent launched after the resume with the same model: "sonnet" override stayed 100% on claude-sonnet-5 (75/75 assistant turns), yet /status still displayed it as Fable — the display appears to show the session model, not the subagent's actual model.
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▎ Expected: per-call model overrides survive session resume; /status reflects the subagent's actual model. Impact:

Environment Info

• Platform: linux
• Terminal: xterm-256color
• Version: 2.1.199
• Feedback ID: 652b4b02-ac9a-4f49-8052-f204609e0a28

Errors

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