Generate system instructions from chat history

[gyanu2507]

Fixes #357

System instructions currently have to be written from scratch, even when the chat already made it obvious how the user wants the agent to behave.

This adds a From chat button on the session header. It drafts instructions from the transcript, you can edit them in a dialog, and nothing is saved until you apply. Inline chats can apply the draft to that session. Named/registry agents only get copy, so we don't mutate the saved agent.

Short chats return 422 before we call the model, so a "hey"/"hi" conversation doesn't turn into a generic helpful-assistant prompt.

New route: POST /api/v1/sessions/{session_id}/generate-instructions

It only returns a suggestion (instructions, current_instructions, sources). Saving still goes through the existing session update.

I didn't regenerate the SDK. The UI adapter hits the new path with client.fetch.

---

Note

Medium Risk
New session-scoped LLM endpoint reads full chat transcripts and can change agent instructions on apply, though access is creator-only and apply reuses existing session update paths.

Overview
Adds From chat in the session header to draft system instructions from the conversation transcript. Opening it calls a new POST /api/v1/sessions/{session_id}/generate-instructions endpoint that returns a suggestion only (instructions, current_instructions, sources); nothing is persisted until the user applies via the existing session update.

The backend builds a bounded transcript from session events, rejects thin chats with 422 before any model call (user-text threshold, generic-output filtering), then uses the session’s configured model to draft instructions. The UI shows an editable modal with source excerpts; Apply to this chat is limited to mutable inline sessions, while chats bound to saved agents get Copy only. The Harness UI adapter exposes this through an optional generateInstructionsFromChat server method (raw client.fetch, SDK not regenerated).

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🦋 Changeset detected

Latest commit: 3e93b29

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@truefoundry/trueforge	Patch
@truefoundry/trueforge-ui	Patch

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[gyanu2507]

Merged current main into this branch.

Conflicts were in the chat chrome and harness adapter. GenerateInstructionsButton stays next to Save. Save still hides while agent config is open (SaveAgentForm / SaveAgentFormFields from main). createHarnessChatServer keeps generateInstructionsFromChat on the typed server from main.

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