docs+installer: how to register mempalace with opencode MCP, probe for it

Two missing pieces bundled here:

1. The README described the MCP server wrapper (mempalace-mcp-server,
   a 3-line shell script that exec's the venv's python) as the
   canonical answer on a uv-tool install. That is over-engineered and
   out of step with the live reference box: opencode.json there uses
   ['mempalace-mcp'] directly, which is the shim uv tool install
   already creates. Rewrote the section to put the simple canonical
   answer first and demote the wrapper to a legacy-fallback sidebar.

   New 'Registering mempalace with opencode' section covers:
   - The one-entry JSON stanza to paste into the mcp object.
   - A full minimal opencode.json for someone starting fresh (with
     the 'instructions' array pointing at the wake-up protocol).
   - Custom palace path variant.
   - Claude Code one-liner (claude mcp add mempalace -- mempalace-mcp).
   - Pointer at 'mempalace mcp' subcommand which prints the currently-
     recommended snippets — useful when upstream updates conventions.
   - Troubleshooting table (tools absent / server unavailable /
     ModuleNotFoundError) with per-symptom fixes.

   The legacy-fallback subsection explains what the wrapper script
   was for (the pip-install → uv-tool-install transition era), shows
   its 3-line implementation for completeness, and is explicit about
   not using it for new installs.

   Verification checklist updated: now runs 'which mempalace-mcp' and
   'mempalace-mcp --help' against the shim, not the wrapper.

2. install.sh gains a matching probe: after the existing wake-up
   protocol check, it grep-checks ~/.config/opencode/opencode.json
   for 'mempalace' + 'mempalace-mcp' substrings. Present → clean
   success line. Missing → actionable warning that prints the exact
   JSON stanza to add plus a pointer to the README anchor and the
   'mempalace mcp' CLI helper. Skipped when opencode.json doesn't
   exist (non-opencode hosts).

   Textual grep rather than strict JSON parse: we don't want to
   hard-depend on python/jq at install time, and the two substrings
   together are specific enough to avoid false positives.

   Prerequisites list gets a 5th bullet flagging MCP registration as
   required and pointing at the new section + the installer probe.

Smoke-tested both scenarios on the reference box — config with
mempalace entry present (all ticks green), config with entry removed
(actionable warning, correct snippet shown), config restored to
original state.

install.sh

@@ -186,6 +186,39 @@ check_wake_up_protocol() {
     return 0
 }
 
+# ── Verify mempalace is registered as an MCP server in opencode.json ──
+# Even with mempalace installed and the wake-up protocol in place, opencode
+# won't actually launch the MCP server (so mempalace_* tools won't appear in
+# the agent's toolset) unless ~/.config/opencode/opencode.json declares a
+# server under .mcp.mempalace with command ["mempalace-mcp"] (or the legacy
+# wrapper equivalent).
+#
+# This is a lightweight textual check — we don't parse JSON strictly, just
+# look for the expected substring. False negatives are acceptable (a weirdly
+# formatted but valid config), false positives less so but very unlikely
+# given the specific shim name. Skipped on non-opencode hosts.
+check_opencode_mcp() {
+    local opencode_config="$HOME/.config/opencode/opencode.json"
+    [[ -f "$opencode_config" ]] || return 0   # no config → nothing to check
+
+    if grep -q '"mempalace"[[:space:]]*:' "$opencode_config" 2>/dev/null \
+       && grep -q 'mempalace-mcp' "$opencode_config" 2>/dev/null; then
+        ok "mempalace MCP server registered in opencode.json"
+        return 0
+    fi
+
+    warn "mempalace MCP server NOT registered in $opencode_config"
+    printf '       Without this, opencode loads the skill but no mempalace_* tools\n'
+    printf '       are reachable at runtime, so search/diary/KG calls silently fail.\n'
+    printf '       Add this entry under the top-level "mcp" object:\n'
+    printf '           "mempalace": { "type": "local", "command": ["mempalace-mcp"] }\n'
+    printf '       Or open a fresh config with:\n'
+    printf '           mempalace mcp     # prints current recommended snippets\n'
+    printf '       Full details (including Claude Code one-liner) in:\n'
+    printf '           README.md#registering-mempalace-with-opencode-or-other-mcp-clients\n'
+    return 0
+}
+
 do_install() {
     echo
     echo "mempalace-toolkit installer"
@@ -205,6 +238,8 @@ do_install() {
     echo
     check_wake_up_protocol
     echo
+    check_opencode_mcp
+    echo
     ok "Done."
     echo
     echo "Next: ./bin/mempalace-session --dry-run"