feat(unstable-v2): add cancelled variant to tool call and plan item statuses

[benbrandt]

No description provided.

[Copilot]

Pull request overview

Adds a new cancelled lifecycle state for both v2 tool calls and v2 plan items, updating the JSON schemas, Rust schema types, v1↔v2 conversion behavior, and protocol documentation to describe the new status.

Changes:

• Add cancelled to ToolCallStatus and PlanEntryStatus in both stable and unstable v2 JSON schemas.
• Update v2 protocol docs (including migration + draft docs) to document the new cancelled status.
• Update Rust v2 schema enums + tests, and ensure v2→v1 conversion correctly errors on the new unrepresentable v2 status.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
schema/v2/schema.unstable.json	Adds cancelled to unstable v2 tool-call and plan-entry status enums.
schema/v2/schema.json	Adds cancelled to stable v2 tool-call and plan-entry status enums.
docs/rfds/v2/tool-call-updates.mdx	Clarifies v2→v1 conversion wording for tool-call updates.
docs/rfds/v2/plan-variants.mdx	Clarifies when v2 item-based plan updates can be lossily represented in v1.
docs/protocol/v2/tool-calls.mdx	Documents cancelled as a tool-call status in stable v2 docs.
docs/protocol/v2/schema.mdx	Documents cancelled for plan-entry and tool-call statuses in the rendered schema docs.
docs/protocol/v2/migration.mdx	Updates migration guidance to note cancelled was added to status.
docs/protocol/v2/draft/tool-calls.mdx	Documents cancelled as a tool-call status in draft v2 docs.
docs/protocol/v2/draft/schema.mdx	Documents cancelled for plan-entry and tool-call statuses in the draft rendered schema docs.
docs/protocol/v2/draft/agent-plan.mdx	Adds cancelled to the documented plan-entry status list (draft).
docs/protocol/v2/agent-plan.mdx	Adds cancelled to the documented plan-entry status list (stable).
agent-client-protocol-schema/src/v2/tool_call.rs	Adds ToolCallStatus::Cancelled + serde roundtrip test.
agent-client-protocol-schema/src/v2/plan.rs	Adds PlanEntryStatus::Cancelled + serde roundtrip test.
agent-client-protocol-schema/src/v2/conversion.rs	Ensures v2→v1 conversion errors for cancelled and adds coverage.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.