Keep the Planner's workspace instructions neutral

Drop the full Atomic session framing and the tool inventory from the
Planner's workspace instructions; the system prompt already lists its
tools. Keep only what the model cannot infer: questions from
ask_user_question and workflows appear as Decisions, and an expired
question means proceeding on best judgement.

Assistant-model: Claude Opus 5.5
Assistant-workflow: inline
Assistant-duration: 12m converged, estimated 10m
Assistant-verification: bun test passed: apps/server/src/harness, chat and agent, 302 pass, 0 fail
Assistant-verification: bun run types passed: all workspaces and E2E
Assistant-verification: bun run ci passed: dprint, oxlint, tokens, type scale and design checks
User-preference: Planner prompts stay neutral; no "full Atomic session" meta framing, name tools only where it adds information the system prompt lacks
Co-authored-by: Alex Lavaee <lavaman131@github.com>