feat(ingestion): add pipeline orchestrator with prompt builder

Adds prompt.go (BuildPrompt + systemPrompt) and pipeline.go (Run, Config,
Result, mergeAll) that wire chunking, LLM calls, parse, merge, index rebuild,
and log append into a single ingestion pipeline. Includes integration tests
covering write, dry-run, and duplicate-path merge scenarios.

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

ingestion/internal/pipeline/pipeline.go

@@ -0,0 +1,120 @@
+// ingestion/internal/pipeline/pipeline.go
+package pipeline
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/wiki"
+)
+
+// CompleteFunc is the function signature for LLM calls.
+type CompleteFunc func(ctx context.Context, system, user string) (string, error)
+
+// Config holds pipeline configuration.
+type Config struct {
+	Complete  CompleteFunc
+	ChunkSize int    // 0 = no chunking
+	Schema    string // overrides brain/CLAUDE.md when set (useful in tests)
+}
+
+// Result is the outcome of a pipeline run.
+type Result struct {
+	Pages    []string // relative paths written (or would-be written in dry-run)
+	Warnings []string
+}
+
+// Run ingests content and writes structured wiki pages to brainDir/wiki/.
+// In dry-run mode, pages are returned but not written to disk.
+func Run(ctx context.Context, cfg Config, brainDir, content, source string, dryRun bool) (Result, error) {
+	inventory, err := wiki.LoadInventory(brainDir)
+	if err != nil {
+		return Result{}, fmt.Errorf("load inventory: %w", err)
+	}
+
+	schema := cfg.Schema
+	if schema == "" {
+		schema = loadSchema(brainDir)
+	}
+
+	chunks := Chunk(content, cfg.ChunkSize)
+
+	var allPages []wiki.Page
+	var allWarnings []string
+
+	for _, chunk := range chunks {
+		userPrompt := BuildPrompt(schema, source, chunk, inventory)
+		output, err := cfg.Complete(ctx, systemPrompt, userPrompt)
+		if err != nil {
+			return Result{}, fmt.Errorf("LLM call: %w", err)
+		}
+		pages, warnings := ParsePages(output)
+		allPages = append(allPages, pages...)
+		allWarnings = append(allWarnings, warnings...)
+	}
+
+	merged := mergeAll(allPages)
+
+	date := time.Now().UTC().Format("2006-01-02")
+	var written []string
+
+	for _, page := range merged {
+		if !dryRun {
+			dest := filepath.Join(brainDir, filepath.FromSlash(page.Path))
+			if err := os.MkdirAll(filepath.Dir(dest), 0o755); err != nil {
+				return Result{}, fmt.Errorf("mkdir for %s: %w", page.Path, err)
+			}
+			if err := os.WriteFile(dest, []byte(page.Content), 0o644); err != nil {
+				return Result{}, fmt.Errorf("write %s: %w", page.Path, err)
+			}
+		}
+		written = append(written, page.Path)
+	}
+
+	if !dryRun {
+		if err := wiki.RebuildIndex(brainDir, date); err != nil {
+			allWarnings = append(allWarnings, fmt.Sprintf("rebuild index: %v", err))
+		}
+		if err := wiki.AppendLog(brainDir, source, written, allWarnings, date); err != nil {
+			allWarnings = append(allWarnings, fmt.Sprintf("append log: %v", err))
+		}
+	}
+
+	return Result{Pages: written, Warnings: allWarnings}, nil
+}
+
+// mergeAll deduplicates pages by path, merging content from later occurrences.
+func mergeAll(pages []wiki.Page) []wiki.Page {
+	order := make([]string, 0, len(pages))
+	byPath := make(map[string]wiki.Page, len(pages))
+	for _, p := range pages {
+		if _, seen := byPath[p.Path]; !seen {
+			order = append(order, p.Path)
+			byPath[p.Path] = p
+		} else {
+			byPath[p.Path] = wiki.Merge(byPath[p.Path], p)
+		}
+	}
+	result := make([]wiki.Page, 0, len(order))
+	for _, path := range order {
+		result = append(result, byPath[path])
+	}
+	return result
+}
+
+const defaultSchema = `# Brain Wiki Schema
+Three page types: wiki/sources/, wiki/concepts/, wiki/entities/.
+See brain/CLAUDE.md for the full schema.
+`
+
+func loadSchema(brainDir string) string {
+	b, err := os.ReadFile(filepath.Join(brainDir, "CLAUDE.md"))
+	if err != nil {
+		return defaultSchema
+	}
+	return strings.TrimSpace(string(b))
+}