feat(pipeline): write into wiki/<wing>/{sources,facts}/ when Config.Wing is set (#205 S2)

Sources -> wiki/<wing>/sources, concepts/entities -> wiki/<wing>/facts with
kind: frontmatter; inventory, title resolution and back-references are
confined to the target wing. Empty Wing keeps the retired layout unchanged.
Mutation-checked: widening the inventory beyond the wing fails the
cross-wing back-reference test; a non-plain wing name is rejected.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ingestion/internal/pipeline/pipeline.go

@@ -7,6 +7,7 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 	"io/fs"
 	"os"
@@ -26,6 +27,11 @@ type Config struct {
 	Complete  CompleteFunc
 	ChunkSize int    // 0 = no chunking
 	Schema    string // overrides brain/schema.md when set (useful in tests)
+
+	// Wing, when set, writes into wiki/<wing>/{sources,facts}/ and scopes the
+	// inventory (title resolution, back-references) to that wing alone. Empty
+	// keeps the retired wiki/{sources,concepts,entities}/ layout.
+	Wing string
 }
 
 // Result is the outcome of a pipeline run.
@@ -42,7 +48,16 @@ type Result struct {
 // 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 cfg.Wing != "" && brain.Sanitise(cfg.Wing) != cfg.Wing {
+		return Result{}, fmt.Errorf("invalid wing %q: must be a plain lower-case wing name", cfg.Wing)
+	}
+	var inventory map[wiki.PageType][]wiki.Entry
+	var err error
+	if cfg.Wing != "" {
+		inventory, err = wiki.LoadWingInventory(brainDir, cfg.Wing)
+	} else {
+		inventory, err = wiki.LoadInventory(brainDir)
+	}
 	if err != nil {
 		return Result{}, fmt.Errorf("load inventory: %w", err)
 	}
@@ -60,7 +75,7 @@ func Run(ctx context.Context, cfg Config, brainDir, content, source string, dryR
 	// The merge is already idempotent (#103), so this is cost and signal, not
 	// correctness — which is why it is safe for it to be an early return.
 	bodyHash := hashBody(content)
-	if !dryRun && bodyHash != "" && bodyHash == storedSourceHash(brainDir, sourceSlug) {
+	if !dryRun && bodyHash != "" && bodyHash == storedSourceHash(brainDir, cfg.Wing, sourceSlug) {
 		return Result{Skipped: true, Warnings: []string{
 			fmt.Sprintf("source %q unchanged since last ingest (hash %s) — extraction skipped", source, bodyHash[:12]),
 		}}, nil
@@ -71,7 +86,7 @@ func Run(ctx context.Context, cfg Config, brainDir, content, source string, dryR
 	// only exists once the model has produced a title. So page-aware
 	// extraction (#106) is scoped to the source page: it's the one page every
 	// chunk's prompt can be given in advance.
-	existingPage := readSourcePage(brainDir, sourceSlug)
+	existingPage := readSourcePage(brainDir, cfg.Wing, sourceSlug)
 
 	chunks := Chunk(content, cfg.ChunkSize)
 
@@ -93,7 +108,7 @@ func Run(ctx context.Context, cfg Config, brainDir, content, source string, dryR
 	meta.BodyHash = bodyHash
 	applySourceMeta(allRaw, meta)
 
-	return buildAndWrite(ctx, allRaw, sourceSlug, date, brainDir, source, inventory, allWarnings, dryRun)
+	return buildAndWrite(ctx, cfg.Wing, allRaw, sourceSlug, date, brainDir, source, inventory, allWarnings, dryRun)
 }
 
 // RunRaw runs the pipeline on pre-parsed RawPages, skipping the LLM extraction
@@ -112,12 +127,12 @@ func RunRaw(ctx context.Context, brainDir, source string, rawPages []RawPage, dr
 	sourceSlug := wiki.Slug(source)
 	date := time.Now().UTC().Format("2006-01-02")
 
-	return buildAndWrite(ctx, rawPages, sourceSlug, date, brainDir, source, inventory, nil, dryRun)
+	return buildAndWrite(ctx, "", rawPages, sourceSlug, date, brainDir, source, inventory, nil, dryRun)
 }
 
 // buildAndWrite runs BuildPages through write for both Run and RunRaw.
-func buildAndWrite(ctx context.Context, rawPages []RawPage, sourceSlug, date, brainDir, source string, inventory map[wiki.PageType][]wiki.Entry, warnings []string, dryRun bool) (Result, error) {
-	pages, buildWarnings := BuildPages(rawPages, sourceSlug, date)
+func buildAndWrite(ctx context.Context, wing string, rawPages []RawPage, sourceSlug, date, brainDir, source string, inventory map[wiki.PageType][]wiki.Entry, warnings []string, dryRun bool) (Result, error) {
+	pages, buildWarnings := BuildPagesIn(wing, rawPages, sourceSlug, date)
 	warnings = append(warnings, buildWarnings...)
 	resolved := Resolve(pages, inventory)
 	canonicalized, linkWarnings := CanonicalizeLinks(resolved, inventory)
@@ -158,7 +173,11 @@ func buildAndWrite(ctx context.Context, rawPages []RawPage, sourceSlug, date, br
 	}
 
 	if !dryRun {
-		if err := wiki.RebuildIndex(brainDir, date); err != nil {
+		if wing != "" {
+			if err := brain.BuildWingIndex(brainDir, wing); err != nil {
+				warnings = append(warnings, fmt.Sprintf("rebuild wing index: %v", err))
+			}
+		} else if err := wiki.RebuildIndex(brainDir, date); err != nil {
 			warnings = append(warnings, fmt.Sprintf("rebuild index: %v", err))
 		}
 		if err := wiki.AppendLog(brainDir, source, written, warnings, date); err != nil {
@@ -193,8 +212,12 @@ func hashBody(content string) string {
 // wiki/sources/<sourceSlug>.md, or "" when it doesn't exist yet.
 // It reads through the brain root, regular files only (hyperguild#157): the
 // content goes into the LLM prompt.
-func readSourcePage(brainDir, sourceSlug string) string {
-	raw, err := readBrainFile(brainDir, "wiki/sources/"+sourceSlug+".md")
+func readSourcePage(brainDir, wing, sourceSlug string) string {
+	rel := "wiki/sources/" + sourceSlug + ".md"
+	if wing != "" {
+		rel = "wiki/" + wing + "/sources/" + sourceSlug + ".md"
+	}
+	raw, err := readBrainFile(brainDir, rel)
 	if err != nil {
 		return ""
 	}
@@ -218,8 +241,8 @@ func readBrainFile(brainDir, rel string) ([]byte, error) {
 // Absence always means "extract". That is the fail-safe direction: a missed
 // skip costs one extraction, while a wrong skip loses an update silently — and
 // silence is the failure mode this repo keeps paying for.
-func storedSourceHash(brainDir, sourceSlug string) string {
-	for _, line := range strings.Split(readSourcePage(brainDir, sourceSlug), "\n") {
+func storedSourceHash(brainDir, wing, sourceSlug string) string {
+	for _, line := range strings.Split(readSourcePage(brainDir, wing, sourceSlug), "\n") {
 		if key, value, found := strings.Cut(line, ":"); found && strings.TrimSpace(key) == "source_hash" {
 			return strings.TrimSpace(value)
 		}