feat(brain): add Query client for skill handler context injection

internal/brain/client.go

@@ -0,0 +1,76 @@
+// internal/brain/client.go
+// Package brain provides a lightweight client for querying the ingestion server.
+// Skill handlers call Query before spawning workers to inject relevant knowledge
+// from the brain into the task prompt. Errors are suppressed — the brain is
+// optional context; its absence must never block a skill invocation.
+package brain
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"strings"
+)
+
+type queryResult struct {
+	Path    string `json:"path"`
+	Title   string `json:"title"`
+	Excerpt string `json:"excerpt"`
+	Score   int    `json:"score"`
+}
+
+// Query calls the ingestion server and returns relevant knowledge as a
+// formatted string ready to prepend to a worker task prompt.
+// Returns empty string (no error) when baseURL or query is empty,
+// when the brain is unreachable, or when no results are found.
+func Query(ctx context.Context, baseURL, query string, limit int) (string, error) {
+	if baseURL == "" || strings.TrimSpace(query) == "" {
+		return "", nil
+	}
+	if limit <= 0 {
+		limit = 3
+	}
+
+	body, _ := json.Marshal(map[string]any{"query": query, "limit": limit})
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, baseURL+"/query", bytes.NewReader(body))
+	if err != nil {
+		slog.Warn("brain: build request failed", "err", err)
+		return "", nil
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		slog.Warn("brain: ingestion server unreachable", "err", err)
+		return "", nil
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusOK {
+		slog.Warn("brain: ingestion server returned non-OK", "status", resp.StatusCode)
+		return "", nil
+	}
+
+	out, _ := io.ReadAll(resp.Body)
+	var result struct {
+		Results []queryResult `json:"results"`
+	}
+	if err := json.Unmarshal(out, &result); err != nil || len(result.Results) == 0 {
+		return "", nil
+	}
+
+	var b strings.Builder
+	b.WriteString("## Relevant knowledge\n\n")
+	for _, r := range result.Results {
+		title := r.Title
+		if title == "" {
+			title = r.Path
+		}
+		fmt.Fprintf(&b, "### %s\n%s\n\n", title, r.Excerpt)
+	}
+	return b.String(), nil
+}