mcp-config: write the sync hook to ~/.zshrc.local, not ~/.zshrc

~/.zshrc is MANAGED: zsh/install.sh overwrites it wholesale (cp) on every
bootstrap run. install.sh appended the mcp-sync hook to that same file, so
the next bootstrap silently deleted it -- sync.sh then never ran, so
OPENCODE_CONFIG was never exported and opencode came up with no models and
no skills. It looked like a broken gateway or a bad model; it was a wiped
shell hook.

~/.zshrc.local is the unmanaged file the managed zshrc sources last, so the
hook now survives a re-bootstrap. Verified: hook lands in ~/.zshrc.local
(0600), managed ~/.zshrc is left untouched, and OPENCODE_CONFIG still
exports after simulating the bootstrap overwrite.

Also warn instead of failing silently when python3 is missing: sync.sh then
deploys the base config verbatim with an EMPTY models map, which presents as
"the gateway has no models" rather than "a dependency is absent".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mcp-config/sync.sh

@@ -140,8 +140,14 @@ with os.fdopen(fd, "w") as f:
 os.replace(tmp, dest)
 PYEOF
   elif [ -n "$_base" ]; then
+    # No python3: the base config is deployed verbatim, so its "models" map
+    # stays EMPTY and opencode shows the provider with zero models. That looks
+    # like a broken gateway rather than a missing dependency, so say so — this
+    # is the one case worth breaking the silence for.
     mv "$_base" "$MCP_SYNC_DEST" 2>/dev/null || true
     _base=""
+    printf 'mcp-sync: python3 not found — models cannot be discovered.\n' >&2
+    printf 'mcp-sync: install python3 (bootstrap.sh does), then open a new shell.\n' >&2
   fi
   [ -n "$_base" ] && rm -f "$_base"
 }