Boot a session into the THINKER role for the DO-IT pipeline. Use when the user says 'think', '/think', 'thinker session', 'let's spec something out', 'brainstorm X', 'triage these ideas', 'sort this dump', 'collect some bugs', or 'process the done work' — any session whose job is discovery, intake, capture, or review that ends in a spec (or a closed review), not code. A thinker is READ-ONLY on code: never edits files, never touches git. It has four shapes (brainstorm / review / intake-triage / collect) and performs its own handoffs (hand a spec to the orchestrator, send a memo). Stage 2 of the DO-IT pipeline. Invoke at the START of a thinking session.
