v0.9.0

Added

• opencode sessions can drive the sessions beside them. They could already
  report what they were doing; now they can act — list the other sessions, hand
  one a task and wait for its answer, answer one that asked, open a session
  (with a git worktree under it), close one, and read what is in each checkout.
  Claude Code and Codex get those operations as MCP tools lich registers when it
  spawns them; opencode cannot be told about a server on its command line, and a
  plugin there cannot register one either — but it can define tools, so the same
  seven are defined here, under the same names.

  Each one runs the lich binary rather than talking to lich directly, which is
  what keeps every rule about them — what is required, what is refused, what a
  refusal says — in the one place it is written. Nothing is registered outside a
  lich session, and nothing is registered when opencode's plugin package cannot
  be imported; the reports go on working in both cases.