feat: add brain_query and brain_write MCP tools

Adds the brain skill that proxies HTTP calls to the ingestion server,
exposing brain_query (/query) and brain_write (/write) as MCP tools.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/skills/brain/skill.go

@@ -0,0 +1,55 @@
+// internal/skills/brain/skill.go
+package brain
+
+import (
+	"encoding/json"
+
+	"github.com/mathiasbq/supervisor/internal/registry"
+)
+
+// Config holds brain skill configuration.
+type Config struct {
+	IngestBaseURL string // base URL of the ingestion HTTP server, e.g. http://localhost:3300
+}
+
+// Skill implements registry.Skill for brain_query and brain_write.
+type Skill struct {
+	cfg Config
+}
+
+// New constructs a brain Skill.
+func New(cfg Config) *Skill { return &Skill{cfg: cfg} }
+
+// Name returns the skill name used for routing.
+func (s *Skill) Name() string { return "brain" }
+
+// Tools returns the MCP tool definitions for brain_query and brain_write.
+func (s *Skill) Tools() []registry.ToolDef {
+	schema := func(required []string, props map[string]any) json.RawMessage {
+		b, _ := json.Marshal(map[string]any{"type": "object", "required": required, "properties": props})
+		return b
+	}
+	str := map[string]any{"type": "string"}
+	num := map[string]any{"type": "integer"}
+
+	return []registry.ToolDef{
+		{
+			Name:        "brain_query",
+			Description: "Search the hyperguild brain wiki for relevant knowledge. Call this before starting any significant task.",
+			InputSchema: schema([]string{"query"}, map[string]any{
+				"query": str,
+				"limit": num,
+			}),
+		},
+		{
+			Name:        "brain_write",
+			Description: "Write a raw knowledge note to the brain for later ingestion into the wiki.",
+			InputSchema: schema([]string{"content"}, map[string]any{
+				"content":  str,
+				"type":     str,
+				"domain":   str,
+				"filename": str,
+			}),
+		},
+	}
+}