Expose discovered MCP tools through the act allowlist (#251)

Second half of the MCP client: the tools the manager discovers become rows in
the existing act allowlist instead of a parallel capability system.

An MCP tool is encoded in the columns that already exist — cmd
["mcp",<server>,<tool>], scope mcp:<server> — so no migration, and
ProposeTool/EnableTool/DisableTool, tool.Matcher and the confirm turn need no
changes. One branch in Executor.Exec routes such a row to the manager instead
of exec, and "mcp" is never run as a binary.

Discovery only ever PROPOSES. destructive comes from the inverse of the MCP
readOnlyHint, so a tool that does not promise to be read-only inherits the
confirm turn, and enabling stays on /tools behind step-up.

Voice args are positional and MCP args are named, so CallPositional binds only
what it can defend: no required properties runs bare, and a read-only tool with
exactly one required string or number gets the tail. Everything else refuses
with ErrNeedsArgs rather than guessing. The read-only condition was learned
against the live Vikunja server: update_task requires only task_id and takes
the rest as optional, so one guessed argument blanked the fields it did not
mention. A partially-filled write destroys what it omits, so a mutating tool
never receives a guessed argument.

Also: a read-only mcp_servers IPC method and an "MCP servers" card on /tools
showing transport, target and state, with the trust level of a local target
spelled out. There is deliberately no call-a-tool IPC method and no run button,
so mutation keeps exactly one path.

Vikunja #251

cmd/mavweb/handlers_test.go

@@ -67,6 +67,14 @@ type fakeCore struct {
 	// for handleChatAPI tests
 	chatText string
 	chatErr  error
+
+	// for the MCP section of /tools
+	mcpServers []ipc.MCPServerStatus
+	mcpErr     error
+}
+
+func (f *fakeCore) MCPServers(context.Context) ([]ipc.MCPServerStatus, error) {
+	return f.mcpServers, f.mcpErr
 }
 
 func (f *fakeCore) Chat(_ context.Context, text string) (string, error) {
@@ -1118,3 +1126,49 @@ func TestHandleChatAPI_FailOpenByDefault(t *testing.T) {
 		t.Errorf("core.Chat text = %q, want %q", core.chatText, "привет")
 	}
 }
+
+// The MCP section renders the configured servers, and a proposal that already
+// knows its cmd prefills the enable form so the argv is not retyped by hand.
+func TestHandleTools_GET_MCPSection(t *testing.T) {
+	core := &fakeCore{
+		proposed: []ipc.Tool{{
+			Name: "vikunja_list_tasks", Scope: "mcp:vikunja",
+			Cmd: []string{"mcp", "vikunja", "list_tasks"}, Destructive: true,
+			Utterance: "mcp vikunja/list_tasks: List tasks in a project.",
+		}},
+		mcpServers: []ipc.MCPServerStatus{
+			{Name: "vikunja", Transport: "http", Target: "http://192.168.1.104:9100/mcp", Connected: true, Server: "vikunja 0.1.0", Tools: 4},
+			{Name: "files", Transport: "stdio", Target: "mcp-server-fs /srv", Err: "start: no such file"},
+		},
+	}
+	rr := httptest.NewRecorder()
+	handleTools(rr, httptest.NewRequest(http.MethodGet, "/tools", nil), core, nil, false)
+	if rr.Code != http.StatusOK {
+		t.Fatalf("status = %d", rr.Code)
+	}
+	body := rr.Body.String()
+	for _, want := range []string{
+		"MCP servers", "vikunja", "192.168.1.104:9100/mcp", "vikunja 0.1.0",
+		"files", "no such file",
+		`value="mcp vikunja list_tasks"`, // the enable form is prefilled
+		"checked",                        // and pre-marked destructive (no readOnlyHint)
+	} {
+		if !strings.Contains(body, want) {
+			t.Errorf("missing %q in /tools output", want)
+		}
+	}
+}
+
+// MCP off (or an older core that does not know the method) renders the section
+// empty instead of breaking the page.
+func TestHandleTools_GET_MCPUnavailable(t *testing.T) {
+	core := &fakeCore{mcpErr: ipc.ErrNotImplemented}
+	rr := httptest.NewRecorder()
+	handleTools(rr, httptest.NewRequest(http.MethodGet, "/tools", nil), core, nil, false)
+	if rr.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200", rr.Code)
+	}
+	if !strings.Contains(rr.Body.String(), "no MCP servers configured") {
+		t.Error("expected the empty-state copy")
+	}
+}

cmd/mavweb/main.go

@@ -692,7 +692,7 @@ const toolsHTML = `{{template "shellTop" "tools"}}
 {{if .Msg}}<div class="msg msg-ok">{{.Msg}}</div>{{end}}
 <section class=card>
 <h2 class=card-title>proposed <span class=badge>{{len .Proposed}}</span></h2>
-{{if .Proposed}}<p class=hint>maven drafted these from acts she couldn't run. Fill the command (argv, space-separated) and enable.</p>
+{{if .Proposed}}<p class=hint>maven drafted these from acts she couldn't run. Fill the command (argv, space-separated) and enable. A row in an <code>mcp:</code> scope came from an MCP server and already knows what it calls — check the command, then enable.</p>
 <div class=scroll><table><tr><th>name</th><th>scope</th><th>from utterance</th><th>enable as</th></tr>
 {{range .Proposed}}<tr>
 <td><code>{{.Name}}</code></td><td><span class=badge>{{.Scope}}</span></td><td>{{.Utterance}}</td>
@@ -700,8 +700,8 @@ const toolsHTML = `{{template "shellTop" "tools"}}
 <input type=hidden name=name value="{{.Name}}">
 <input type=hidden name=scope value="{{.Scope}}">
 <input type=hidden name=action value=enable>
-<input type=text name=cmd class=input-wide placeholder="systemctl restart" required>
-<label><input type=checkbox name=destructive> destructive</label>
+<input type=text name=cmd class=input-wide placeholder="systemctl restart" value="{{join .Cmd " "}}" required>
+<label><input type=checkbox name=destructive {{if .Destructive}}checked{{end}}> destructive</label>
 <button class=btn>enable</button></form>
 <form method=post action=/tools class=inline-form>
 <input type=hidden name=name value="{{.Name}}">
@@ -730,6 +730,19 @@ const toolsHTML = `{{template "shellTop" "tools"}}
   <div class=hint>enable proposed tools above, or ask maven to configure one</div>
 </div>{{end}}
 </section>
+<section class=card>
+<h2 class=card-title>MCP servers <span class=badge>{{len .MCP}}</span></h2>
+{{if .MCP}}<p class=hint>servers she connects OUT to. Their tools appear above as proposals — a configured server is a place she may look, not a capability she has. A <code>stdio</code> target is a process on this box; an <code>http</code> one on a loopback or LAN address is inside the network, so treat its tools accordingly.</p>
+<div class=scroll><table><tr><th>name</th><th>transport</th><th>target</th><th>state</th><th>tools</th></tr>
+{{range .MCP}}<tr><td><code>{{.Name}}</code></td><td><span class=badge>{{.Transport}}</span></td><td><code>{{.Target}}</code></td>
+<td>{{if .Connected}}connected{{if .Server}} — {{.Server}}{{end}}{{else}}<span class=red>down</span>{{if .Err}} — {{.Err}}{{end}}{{end}}</td>
+<td>{{.Tools}}</td></tr>{{end}}</table></div>
+{{else}}<div class=empty>
+  <svg class=icon width="20" height="20"><use href="/ethos-icons.svg#i-settings"/></svg>
+  <div>no MCP servers configured</div>
+  <div class=hint>add an <code>mcp.servers</code> block to mavend.json to let her use an external tool server</div>
+</div>{{end}}
+</section>
 {{template "shellBottom"}}`
 
 // routinesHTML — proposed routine review surface. One row per thing maven
@@ -1320,12 +1333,20 @@ func handleTools(w http.ResponseWriter, r *http.Request, core ipc.CoreAPI, sessi
 		http.Error(w, "core read failed", http.StatusBadGateway)
 		return
 	}
+	// MCP is off by default and an older core may not know the method at all,
+	// so a failure here renders an empty section rather than breaking the page.
+	servers, err := core.MCPServers(ctx)
+	if err != nil {
+		log.Printf("tools: mcp servers: %v", err)
+		servers = nil
+	}
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
 	if err := toolsTmpl.Execute(w, struct {
 		Msg      string
 		Proposed []ipc.Tool
 		Enabled  []ipc.Tool
-	}{msg, proposed, enabled}); err != nil {
+		MCP      []ipc.MCPServerStatus
+	}{msg, proposed, enabled, servers}); err != nil {
 		log.Printf("tools render: %v", err)
 	}
 }