fix(web): support PostgREST not(col, is) so archived session lists load

Local Postgres not() only handled eq/cs, so archived=1 threw and the sidebar archive view returned 500. Compile is not null/true/false instead of inequality.

frontend/src/lib/db/local-postgres-client-core.ts

@@ -20,6 +20,7 @@ type Filter =
   | Readonly<{ kind: "like"; column: string; value: unknown }>
   | Readonly<{ kind: "in"; column: string; value: readonly unknown[] }>
   | Readonly<{ kind: "is"; column: string; value: unknown }>
+  | Readonly<{ kind: "isNot"; column: string; value: unknown }>
   | Readonly<{ kind: "notContains"; column: string; value: unknown }>
   | Readonly<{ kind: "or"; expression: string }>;
 
@@ -46,6 +47,19 @@ function identifier(value: string): string {
   return `"${normalized}"`;
 }
 
+export function compileUnaryIsClause(
+  column: string,
+  value: unknown,
+  negated: boolean,
+): string {
+  const quoted = identifier(column);
+  const target = value === null ? "null" : value === true ? "true" : value === false ? "false" : null;
+  if (target === null) {
+    throw new Error(negated ? "unsupported not filter" : "unsupported is filter");
+  }
+  return `${quoted} is${negated ? " not" : ""} ${target}`;
+}
+
 export function formatOrderClause(
   ordering: readonly { column: string; ascending: boolean }[],
 ): string {
@@ -388,6 +402,11 @@ class LocalPostgresQueryBuilder implements PromiseLike<QueryResult> {
       this.filters.push({ kind: "neq", column, value });
       return this;
     }
+    if (operator === "is") {
+      compileUnaryIsClause(column, value, true);
+      this.filters.push({ kind: "isNot", column, value });
+      return this;
+    }
     if (operator !== "cs") throw new Error("unsupported not filter");
     this.filters.push({ kind: "notContains", column, value });
     return this;
@@ -451,10 +470,10 @@ class LocalPostgresQueryBuilder implements PromiseLike<QueryResult> {
       }
       const column = identifier(filter.column);
       if (filter.kind === "is") {
-        if (filter.value === null) return `${column} is null`;
-        if (filter.value === true) return `${column} is true`;
-        if (filter.value === false) return `${column} is false`;
-        throw new Error("unsupported is filter");
+        return compileUnaryIsClause(filter.column, filter.value, false);
+      }
+      if (filter.kind === "isNot") {
+        return compileUnaryIsClause(filter.column, filter.value, true);
       }
       if (filter.kind === "in") {
         if (filter.value.length === 0) return "false";