docs(agents): upstream references come from the local grok-build clone

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -11,3 +11,6 @@ node_modules/
 
 # Local test credentials
 cred.md
+
+# Upstream xai-org/grok-build reference clone
+/grok-build/

AGENTS.md

@@ -20,6 +20,11 @@ selectively ported through upstream `77cd7eb` (2026-08-25, ≈v1.0.10) in
 the 0.1.13 cycle, through `3794978` (2026-09-09, ≈v1.0.24) in the 0.1.15
 cycle, through `a28ee2b` (2026-09-17, ≈v1.0.35) in the 0.1.16 cycle, and
 through `2bdd1d6` (2026-09-29, ≈v1.0.45) in the 0.1.19 cycle.
+The local release is 0.1.20; it adds custom providers declared by base
+URL (`[platforms.<name>]`, see CUSTOM PROVIDERS below).
+Every upstream reference comes from the local clone at `./grok-build`
+(gitignored, never committed): `git -C grok-build pull` before a sync,
+then read upstream code and history there, not from the web.
 Upstream is daily "Synced from monorepo" snapshots —
 the commit BODIES carry per-change bullet lists, and
 `crates/codegen/xai-grok-shell/changelogs/` maps releases to dates;