db as source of truth: wiki→seeds, archive old artifacts, knowledge ingestion

- Migrations 010 (content_hash) + 011 (search tsvector column)
- new: internal/knowledge/seed.go — knowledge seed ingest engine
- new: internal/httpapi/knowledge.go — SearchKnowledge + GetEntityKnowledge
- wire knowledge ingest into oikos seed pipeline
- convert all 36 wiki docs + 6 investigations + 12 runbooks → seeds/knowledge.yaml
- archive: knowledge/wiki/→archive/, oikos/cards/→archive/, .hermes/plans/→archive/
- delete: 9 superseded Python kernel files, ledger/, mcp/build_host_files.py
- remove empty knowledge/ directory tree

cmd/oikos/main.go

@@ -14,6 +14,7 @@ import (
 	"github.com/dtoro/oikos/internal/config"
 	"github.com/dtoro/oikos/internal/db"
 	"github.com/dtoro/oikos/internal/httpapi"
+	"github.com/dtoro/oikos/internal/knowledge"
 	"github.com/dtoro/oikos/internal/notifier"
 	"github.com/dtoro/oikos/internal/observability"
 	"github.com/dtoro/oikos/internal/scheduler"
@@ -125,6 +126,7 @@ Roles:
   notifier   Run the notification service (Phase 3)
   all        Run all roles in one process (dev mode)
   secret     Secret management (Phase 5)
+  knowledge  Convert wiki to knowledge seed (one-shot)
   version    Print version info
 
 Environment:
@@ -230,6 +232,32 @@ func runSeed(ctx context.Context, cfg config.Config) error {
 		return err
 	}
 
+	// Ingest knowledge seed (documents, investigations, runbooks)
+	knContent, err := os.ReadFile(seedsDir + "/knowledge.yaml")
+	if err != nil {
+		if os.IsNotExist(err) {
+			slog.Info("knowledge seed not found, skipping")
+		} else {
+			return fmt.Errorf("read knowledge seed: %w", err)
+		}
+	} else {
+		err = pool.SeedIngest(ctx, "knowledge.yaml", knContent,
+			func(ctx context.Context, tx pgx.Tx, data map[string]any) error {
+				r, err := knowledge.Ingest(ctx, tx, data)
+				if err != nil {
+					return err
+				}
+				slog.Info("knowledge ingested",
+					"documents", r.Documents,
+					"investigations", r.Investigations,
+					"runbooks", r.Runbooks)
+				return nil
+			})
+		if err != nil {
+			return err
+		}
+	}
+
 	slog.Info("seed ingest complete")
 	return nil
 }