test(mcp): environment, redaction and end to end through the core

The TZ test checks TZ is absent on Windows: the process policy never sets TZ there (process-environment-hook spec §3). Spec testing bullet and plan updated to match.

docs/superpowers/plans/2026-09-26-mcp-client-playwright.md

@@ -4010,7 +4010,9 @@ public class McpEnvironmentTests
     {
         await using var host = new McpTestHost(Fake(FakeMcp.Server("env")));
         var env = await ServerEnvironmentAsync(host, TimeZoneInfo.FindSystemTimeZoneById("Asia/Tokyo"));
-        Assert.Equal("Asia/Tokyo", env["TZ"]);
+        // The policy skips TZ on Windows, where the OS doesn't use it (process-environment-hook spec §3).
+        if (OperatingSystem.IsWindows()) Assert.False(env.ContainsKey("TZ"));
+        else Assert.Equal("Asia/Tokyo", env["TZ"]);
     }
 
     private sealed class SpawnWatcher : IExtension

docs/superpowers/specs/2026-09-26-mcp-client-playwright-design.md

@@ -365,7 +365,7 @@ No test touches the network, npm or a real browser.
   - environment (`FAKE_MCP_MODE=env`, a tool that returns its environment): with `OPENAI_API_KEY` and `GITHUB_TOKEN`
     in the injected host snapshot, neither reaches the server; a server `env` entry `GITHUB_TOKEN: ${env:GITHUB_TOKEN}`
     delivers it (explicit beats the deny-list); discovery and the session process agree; `TZ` is the session's zone
-    for the session process;
+    for the session process (on Unix; the policy never sets `TZ` on Windows, so there the test checks it's absent);
   - results: text, image → `ImageContent`, oversized image replaced, `isError` → error tool result with content,
     output truncation note;
   - redaction, end to end through the core: the `env` tool's output with a `GITHUB_TOKEN` configured as a secret