added agent instructions drawer

[vinit-truefoundry]

Summary

https://linear.app/truefoundry/issue/FRONTEN-2452/agent-builder-make-instructions-experience-same-as-our-product

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Note

Medium Risk
Changes how agent instructions are edited and persists a new messages field on the agent spec at runtime, which could affect builder save behavior if context and drawer state diverge.

Overview
Replaces the inline instructions textarea in the agent config panel with a summary row (preview + initial user-message count) that opens a dedicated instructions editor.

Adds AgentInstructionsDrawer: a right-side drawer to edit agent instructions and manage initial session user messages (add, edit, remove), with explicit Save (blank messages are dropped; closing without Save discards edits). agentConfigMessages reads/writes spec.messages via SDK-shaped user.message entries until the UI contract exposes them fully.

AgentConfigEditors and AgentConfigDrawerContainer wire the drawer so Save can commit instructions and messages in one updateAgentSpec (container uses onInstructionsSave; editors fall back to onChange when no handler). The component is exported and registered in default slots; tests cover drawer behavior and the integrated commit path.

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Latest commit: b7915c5

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes changesets to release 1 package

Name	Type
@truefoundry/trueforge-ui	Minor

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