feat: add tier and session_log MCP tools

Adds two new MCP skill packages:
- internal/skills/org: exposes the tier tool, calling an injected TierFn
  for testability; returns current operating tier as structured JSON
- internal/skills/sessionlog: exposes the session_log tool, appending
  structured JSONL entries to brain/sessions/{session_id}.jsonl; requires
  session_id, wraps internal/session.Append

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

internal/skills/org/handlers.go

@@ -0,0 +1,21 @@
+// internal/skills/org/handlers.go
+package org
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+)
+
+// Handle dispatches the tier tool call.
+func (s *Skill) Handle(ctx context.Context, tool string, args json.RawMessage) (json.RawMessage, error) {
+	if tool != "tier" {
+		return nil, fmt.Errorf("unknown org tool: %s", tool)
+	}
+	info := s.cfg.TierFn(ctx)
+	b, err := json.Marshal(info)
+	if err != nil {
+		return nil, fmt.Errorf("marshal tier info: %w", err)
+	}
+	return b, nil
+}

internal/skills/org/handlers_test.go

@@ -0,0 +1,29 @@
+// internal/skills/org/handlers_test.go
+package org_test
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+
+	"github.com/mathiasbq/supervisor/internal/skills/org"
+	"github.com/mathiasbq/supervisor/internal/tier"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHandle_Tier_ReturnsTierInfo(t *testing.T) {
+	s := org.New(org.Config{
+		TierFn: func(ctx context.Context) tier.Info {
+			return tier.Info{Tier: tier.LANOnly, Label: "lan-only", ManagedAgents: false}
+		},
+	})
+	out, err := s.Handle(context.Background(), "tier", nil)
+	require.NoError(t, err)
+
+	var info tier.Info
+	require.NoError(t, json.Unmarshal(out, &info))
+	assert.Equal(t, tier.LANOnly, info.Tier)
+	assert.Equal(t, "lan-only", info.Label)
+	assert.False(t, info.ManagedAgents)
+}

internal/skills/org/skill.go

@@ -0,0 +1,40 @@
+// internal/skills/org/skill.go
+package org
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/mathiasbq/supervisor/internal/registry"
+	"github.com/mathiasbq/supervisor/internal/tier"
+)
+
+// TierFn returns the current tier. Injected for testability.
+type TierFn func(ctx context.Context) tier.Info
+
+// Config holds org skill configuration.
+type Config struct {
+	TierFn TierFn
+}
+
+// Skill implements registry.Skill for the tier tool.
+type Skill struct {
+	cfg Config
+}
+
+// New constructs an org Skill.
+func New(cfg Config) *Skill { return &Skill{cfg: cfg} }
+
+// Name returns the skill name.
+func (s *Skill) Name() string { return "org" }
+
+// Tools returns the MCP tool definitions.
+func (s *Skill) Tools() []registry.ToolDef {
+	return []registry.ToolDef{
+		{
+			Name:        "tier",
+			Description: "Returns the current operating tier: 1=full-online (Claude+Ollama+Managed Agents), 2=lan-only (Ollama only), 3=airplane (minimal). Call at session start to know which models and capabilities are available.",
+			InputSchema: json.RawMessage(`{"type":"object","properties":{}}`),
+		},
+	}
+}