Tools-by-code, configurable provider fallback, and unified agent scheduling

Features

• Tools-by-code: Define tools as scripts stored in the platform. Supports team-scoped scripts, keyword tagging, ranked discovery, MCP dot-notation job references, and a new UI for browsing and prompting tool definitions.
• Configurable provider fallback graph (AUX-145): Provider routing now supports a user-defined fallback graph, allowing fine-grained control over which providers are tried when a primary provider is unavailable or rate-limited.
• Unified agent scheduling (AUX-89): Merged cron and deferred scheduling into a single unified system. Closed gaps in agent-facing scheduling UX, surfaced channel context in the system prompt for all agent sessions, and improved script update and discovery flows.
• GPU/CLI policy propagation: Policy updates for GPU and CLI execution are now pushed to connected workers in real time.

Improvements

• Expanded pass() support and improved engineer prompts for tools-by-code workflows.
• Provider fallback now correctly surfaces routed CLI model selection on the wire.

Fixes

• Coordinator now returns errors for blocked RunDirectToolCall invocations so the sandbox correctly receives and throws them.
• Streaming tool call rounds are merged into a single accordion in the chat UI instead of rendering as separate entries.
• Chat view scrolls to show the queued assistant row immediately after sending a message.
• Rate limit and queued state handling corrected in chat, including the routed CLI model being sent correctly.
• System health activity log collapses datasource refresh start/end events into a single row.
• Dashboard grid layout, inline data rendering, and tools-by-code prompt display fixed.

Internal

• Design system contracts audited and UI alignment updated across components.
• Removed dead tool-click event emit from ThreadMessage.