say how to pick up the parity doc cold

Phases 0 and 1 are implementable as written; phase 2 is a decision and should not be handed over as
work. More importantly: reproduce each defect before fixing it. The B-list came from read-only surveys
and only the event-path claim was re-verified at source — one of those surveys reasoned from a dead file
for part of its report, so a confident inventory here is not the same as a checked one.

B1 is the cheap provenance test: open /chat and look. Either no OpenCode session is listed, which
confirms the survey was reading the current tree, or one is, and the whole list needs re-checking.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/opencode-parity.md

@@ -181,6 +181,30 @@ Each phase is independently shippable. Nothing here is a big-bang rewrite.
 
 ---
 
+## If you are picking this up cold
+
+Phases 0 and 1 are ready to implement as written. Phase 2 is a **decision**, not a task — do not start it
+as work.
+
+**Reproduce each defect before fixing it.** The B-list came from read-only surveys, and one of those
+surveys reasoned from a dead file for part of its report (see below). Only the event-path claim was
+re-verified at source. Every B item names its files and lines; open them and confirm the defect is real
+and still present before changing anything. A "fix" to something that was never broken is worse than the
+defect, because the next reader will trust it.
+
+Two that are worth extra care:
+
+- **B2** is a six-hop chain from `ChatDetailPanel` down to `isClaudeModel`. Confirm the whole chain
+  rather than the endpoints — it is the kind of claim that is right in outline and wrong about which hop
+  drops the value.
+- **B1** implies OpenCode sessions are invisible in the UI today. That is trivially checkable by opening
+  `/chat` and looking. Do that first: it either confirms the whole B-list's provenance in one glance, or
+  tells you the surveys were working from a stale tree.
+
+This machine and the home-lab server run the same repo but not necessarily the same OpenCode binary.
+Both `runner.ts:38` and `client.ts:170` pin behaviour to "verified against opencode 1.17.9" with nothing
+enforcing it, so check the installed version before trusting any NDJSON shape in here.
+
 ## Two things to verify before trusting any of this
 
 - The surveys initially disagreed about which file is the live event path. **`runner.ts:174-214` is