Track upstream ACP session injection dependencies

[danielkov]

Kit #24 lands ACP v2 session injection using pinned implementation branches while the protocol and SDK work is reviewed upstream.

Upstream work

• RFD: docs(rfd): mid-turn input via session/inject (queue and steer) agentclientprotocol/agent-client-protocol#1261
• Protocol schema: feat(unstable-v2): add session injection schema agentclientprotocol/agent-client-protocol#2043
• Rust SDK response receipts: feat(jsonrpc): add tracked response receipts agentclientprotocol/rust-sdk#338
• Rust SDK injection support: feat(unstable-v2): add session injection support agentclientprotocol/rust-sdk#339
• AgentKit ACP v2 foundation: feat(acp): add opt-in ACP v2 runtime foundation danielkov/agentkit#12
• AgentKit injection implementation: feat(acp): add unstable v2 session injection danielkov/agentkit#13

Kit follow-up

• Replace the schema fork pin with an upstream release
• Replace the Rust SDK fork pin with upstream releases
• Replace the AgentKit fork patches with released crates
• Remove the temporary [patch.crates-io] entries
• Confirm all ACP and AgentKit packages resolve to one source identity

Kit implementation: #24

Current pins:

• Schema: 6e7e044f9464c4fd652d90699a09e9edc8b3bbad
• Rust SDK: 2f039993d1d6ed8da35b38c31f54a7cbb7338c70
• AgentKit: 4299f31ec1455ea8ee4c46b4dce8e5bec4fdc597