Document the Claude sandbox Haku roadmap

[agentydragon-agent]

Summary

Trim the Claude sandbox → Haku roadmap around the simpler runtime boundary now intended:

• one Console conversation owns one SandboxClaim, one ClaudeSDKClient, and one Claude CLI process
• the sandbox receives a clone of haku-state and uses Git for durability
• trusted Console code owns Agent SDK orchestration, hooks, policy integration, and the pointer back to the standard Haku Console MCP server
• Ducktape owns immutable security/lifecycle enforcement; haku-state owns Haku's evolvable memory, operating context, and UI/source

The roadmap no longer tries to prescribe five detailed PRs before the first useful Haku wake. It now has three work areas:

1. bootstrap a current haku-state checkout with Haku's existing Forgejo authority, a pinned working directory, visible revision/upstream state, and conversation-specific branches
2. load a versioned Haku entrypoint from the checkout's starting revision and add bounded Git lifecycle guidance/hooks
3. harden reconnect, transcript retention, expiry, telemetry, and complete tool-origin projection after the basic wake works

The older Agent SDK plan is reduced to a compact feasibility/transport record rather than duplicating the active roadmap. haku/PLAN.md now keeps only the broader post-runtime product directions.

Validation

• rebased onto origin/devel at 3b1eed43
• one documentation commit: 047ca323
• git diff --check
• Prettier passes for all three files
• all local Markdown links resolve
• standard pre-commit formatting hooks pass
• the three known workspace-local Ducktape wrapper hooks remain unavailable outside Bazel because proto.invocation_pb2 is generated only in the Bazel build