chore(gitignore): resolve opencode.json shadow footgun (REQ-INB-35c)

---ci---
project: inboxos
phase: 1
milestone: v1.4
status: execute
wave: 1
task: T9
---/ci---

.gitignore

@@ -23,8 +23,9 @@ pip-wheel-meta/
 # Local opencode CLI install (used for offline testing of opencode 1.15.13)
 .tools/
 
-# Local opencode config (per-checkout)
-opencode.json
+# v1.4 REQ-INB-35c: opencode.json is TRACKED in git (not ignored).
+# The .gitignore line was removed; the file is the canonical config.
+# To switch model pin, edit opencode.json directly and commit.
 
 # Pipeline runtime artifacts
 pipelines/_artifacts/