Reduce host capacity headroom and remove learned usage padding

src/lib/server/hosts/schema.ts

@@ -57,6 +57,7 @@ export function ensureHostSchema(handle: Database.Database): void {
         CREATE TABLE IF NOT EXISTS ec_resource_allowances (
             scope TEXT NOT NULL, phase TEXT NOT NULL, cpu_cores REAL NOT NULL, memory_bytes REAL NOT NULL,
             samples INTEGER NOT NULL, window_start TEXT NOT NULL, observed_at TEXT NOT NULL, computed_at TEXT NOT NULL,
+            usage_margin REAL NOT NULL DEFAULT 1,
             PRIMARY KEY(scope,phase)
         );
         CREATE TABLE IF NOT EXISTS ec_host_decommissions (
@@ -71,5 +72,14 @@ export function ensureHostSchema(handle: Database.Database): void {
     if (!columns.some(column => column.name === 'last_delivered_at')) handle.exec('ALTER TABLE ec_host_operations ADD COLUMN last_delivered_at TEXT');
     const hostColumns = handle.prepare('PRAGMA table_info(ec_hosts)').all() as { name: string }[];
     if (!hostColumns.some(column => column.name === 'deleted_at')) handle.exec('ALTER TABLE ec_hosts ADD COLUMN deleted_at TEXT');
+    const allowanceColumns = handle.prepare('PRAGMA table_info(ec_resource_allowances)').all() as { name: string }[];
+    if (!allowanceColumns.some(column => column.name === 'usage_margin')) {
+        // Existing caches include 25% padding. Preserve learned evidence while
+        // removing that padding exactly once, including dormant startup models.
+        handle.transaction(() => {
+            handle.exec('ALTER TABLE ec_resource_allowances ADD COLUMN usage_margin REAL NOT NULL DEFAULT 1');
+            handle.exec('UPDATE ec_resource_allowances SET cpu_cores=cpu_cores/1.25, memory_bytes=CAST(memory_bytes/1.25 AS INTEGER)');
+        })();
+    }
     initialized.add(handle);
 }