feat(seats): memory, the Playwright MCP config, and the seats library

:Memory: MemAvailable and the reserve policy, the sampler of a pass's peak
tree PSS (one sweep, a pause of three sweeps at least, stopped with the
driver), and the calibration file every driver on the machine shares,
re-read and written under its lock.

:Mcp: the pinned @playwright/mcp 0.0.83 arguments and the --mcp-config of
one pass, compact and in a fixed key order.

:Seats: the dotenv loader (token lines only, TOKEN7 inert), the one-word
probe (run under the supervisor, a missing binary reported with its errno
text), the window maths, the ranking, the Fable merge, the editor-bundle
lookup of the claude binary, the redaction of anything token-shaped, and
the report. This libc++ has no tzdb, so a zone by name converts through
the C library with TZ set, reading the system's zoneinfo.

tests/Seats: 92 checks against reference vectors, numbered in order, all
green.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

interfaces/Crafter.Review-Mcp.cppm

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®
+
+export module Crafter.Review:Mcp;
+import std;
+import :Json;
+
+// The Playwright MCP server a lens with the browser environment drives the
+// application with (2026-10-15): one server per pass, launched by the CLI
+// from --mcp-config (never from the lens's Bash), headless, an in-memory
+// profile, its screenshots under the pass's own output dir in the scratch
+// tree. The tools are allowlisted by name (:Tools); browser_run_code_unsafe
+// runs arbitrary Node code in the server's process and is denied.
+export namespace Crafter::Review::Mcp {
+    // @playwright/mcp, verified 2026-10-15 with CLI 2.1.300.
+    constexpr std::string_view PlaywrightMcpVersion = "0.0.83";
+    // The Chromium build that version's Playwright drives, as `npx playwright
+    // install chromium` puts it under ~/.cache/ms-playwright: what
+    // `crafter-review browser install` provides.
+    constexpr std::string_view ChromiumRevision = "1247";
+    // --browser chromium: Playwright's own Chromium; without it the server
+    // wants the `chrome` channel, Google Chrome at /opt/google/chrome
+    // (2026-10-15: every navigate of the second firing run failed on it).
+    std::vector<std::string> DefaultArgs();
+
+    // The --mcp-config value for one pass: the consumer's command and args (the
+    // pipeline's pinned default when the config names none) plus this pass's
+    // output dir.
+    Json PlaywrightConfig(const Json& functional, const std::string& outputDir);
+    // The config as compact JSON (DumpCompact), keys in their order.
+    std::string ConfigJson(const Json& config);
+    // <scratch>/playwright/<label with / and spaces as _>, made.
+    std::filesystem::path OutputDir(const std::filesystem::path& scratch, std::string_view label);
+}