docs(steam): record the real onboarding state — a wait on Valve, not a task

The docs described Steamworks onboarding as pending work. It is pending VALVE: the partner account
exists, identity verification is under review, and the tax interview is in their queue with a quoted
turnaround of up to 30 business days. No app IDs are assigned, no store page exists, and Release
entitlement therefore still fails closed — by design.

Distribution.md §2 becomes a status table plus the critical path computed from Valve's own published
windows (30 business days verification → fee/app IDs → up to 12 business days store review → page
public ≥2 weeks before release → up to 12 business days build review). Earliest realistic launch:
early-to-mid February 2027, leaving ~7 weeks before the 2027-04-01 launch price ends.

Nothing in this blocks the code; commercial.md, TASKS 54 and HANDOFF now say so instead of implying
Steam is an outstanding coding task.

HANDOFF.md

@@ -25,6 +25,10 @@
 - Open loop: `32·4` is proven by construction only — kill ffmpeg mid-recording and play the file.
 - Do not push absent a checkpoint request.
 
+- **Steam is a wait, not a task:** partner account exists, identity verification pending, tax review in
+  Valve's queue (up to 30 business days). No app IDs, no store page, Release entitlement still fails
+  closed. Earliest realistic launch early-to-mid February 2027 — see `Distribution.md` §2.
+
 ## Landmines
 
 - **The preview pane draws frame-source layers from a whitelist of DataTriggers.** A layer type with no