[FEATURE]: Save dynamically generated system prompt to opencode.db so it's included in transcript exports #26376

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Currently, the dynamically generated system prompt (instructions) is built in-memory before the LLM call and is not persisted in the opencode.db SQLite database. Because of this, it is omitted when exporting a session transcript, making it difficult to debug custom instructions or agent behavior without a network proxy or debug logs.

Request:
Persist the dynamically generated system prompt into the message table (e.g., as role: "system") at session initialization. This would allow the existing transcript export features to natively include the full system prompt alongside the rest of the conversation history.

Benefits:

• Simplifies debugging of AGENTS.md and custom environment instructions.
• Provides a complete, 1:1 record of the exact instructions the agent received during a session.
• Piggybacks on the existing transcript export mechanism for a clean implementation.