fix: resolve all golangci-lint errors

Fixes 15 pre-existing lint issues:

errcheck (6 issues):
- mol_distill.go: Add _ = for f.Close() and os.Remove()
- routed.go: Add _ = for routedStorage.Close() (4 locations)

gosec (8 issues):
- maintenance.go, routes.go: Add nolint for G304 (file paths from known dirs)
- mol_distill.go: Add nolint for G304 (file creation in known search paths)
- formula.go: Change WriteFile permissions from 0644 to 0600 (G306)
- gate.go: Add nolint for G204 (exec.Command with trusted AwaitID fields)

misspell (1 issue):
- gate.go: Fix "cancelled" -> "canceled" in comment

unparam (2 issues):
- cook.go, controlflow.go: Add nolint for functions returning always-nil error

Also:
- Update pre-commit-hooks to v6.0.0
- Add lint step to "Landing the Plane" session-end protocol

cmd/bd/routed.go

@@ -50,14 +50,14 @@ func resolveAndGetIssueWithRouting(ctx context.Context, localStore storage.Stora
 		// Step 2: Resolve and get from routed store
 		result, err := resolveAndGetFromStore(ctx, routedStorage.Storage, id, true)
 		if err != nil {
-			routedStorage.Close()
+			_ = routedStorage.Close()
 			return nil, err
 		}
 		if result != nil {
-			result.closeFn = func() { routedStorage.Close() }
+			result.closeFn = func() { _ = routedStorage.Close() }
 			return result, nil
 		}
-		routedStorage.Close()
+		_ = routedStorage.Close()
 	}
 
 	// Step 3: Fall back to local store
@@ -133,7 +133,7 @@ func getIssueWithRouting(ctx context.Context, localStore storage.Storage, id str
 	// Step 3: Try the routed storage
 	routedIssue, routedErr := routedStorage.Storage.GetIssue(ctx, id)
 	if routedErr != nil || routedIssue == nil {
-		routedStorage.Close()
+		_ = routedStorage.Close()
 		// Return the original error if routing also failed
 		if err != nil {
 			return nil, err
@@ -148,7 +148,7 @@ func getIssueWithRouting(ctx context.Context, localStore storage.Storage, id str
 		Routed:     true,
 		ResolvedID: id,
 		closeFn: func() {
-			routedStorage.Close()
+			_ = routedStorage.Close()
 		},
 	}, nil
 }