fix(test): keep the microcompact scratch dirs off /tmp when a case fails

Fourteen cases each made their own `mc-` dir. Thirteen removed it on the last
line of the test body, so an assertion that threw skipped the removal; the
fourteenth (case 11) never removed it at all, so that one leaked on the green
path too. None of the fourteen was inside a try/finally — the file's three
`finally` blocks belong to withEnv, silenceStderr and silenceStderrAsync, and
restore env and stderr rather than remove anything.

Measured on this host: 750 `mc-*` dirs in /tmp, the largest single leak this
repo's suite produces. Reproduced two ways — a clean run of the parent leaves 1
dir behind (case 11), and one injected assertion failure leaves 2. After this
change both are 0.

Registering the dir at creation and collecting in after() puts the cleanup in one
place instead of fourteen, and covers the paths that were missing rather than the
thirteen that already worked. The eager `rm` calls stay: they free disk during a
long run, and after() is idempotent with force.

after() does not cover SIGINT, SIGKILL, or a throw at import time — measured. The
first matters: Ctrl-C on a long suite still leaks. The last is vacuous here, since
every mcTemp() call is inside a test body.

test/proxy-wrapper.test.mjs already carries this shape; this is that pattern, not
a new one.

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

Author: codeslake

test/proxy-microcompact-stability.test.mjs

@@ -1,4 +1,4 @@
-import { test } from "node:test";
+import { after, test } from "node:test";
 import assert from "node:assert/strict";
 import { mkdtemp, readFile, rm, stat } from "node:fs/promises";
 import { tmpdir } from "node:os";
@@ -12,6 +12,24 @@ import ext, {
   runMicrocompactStability,
 } from "../proxy/extensions/microcompact-stability.mjs";
 
+// EVERY SCRATCH DIR, EVEN THE RUNS THAT FAIL. Fourteen cases each made their own
+// and thirteen removed it on the last line of the test body, so an assertion
+// that threw skipped the removal — measured, 750 mc-* dirs on one host, and two
+// more per run with a single failure injected. Registering here means the
+// after() below collects what the happy path already collected and what it did
+// not.
+const scratch = [];
+async function mcTemp() {
+  const d = await mkdtemp(join(tmpdir(), "mc-"));
+  scratch.push(d);
+  return d;
+}
+after(async () => {
+  for (const d of scratch) {
+    try { await rm(d, { recursive: true, force: true }); } catch { /* already gone */ }
+  }
+});
+
 // --- Fixture helpers ---
 
 const SENTINEL_BARE = "[Old tool result content cleared]";
@@ -149,7 +167,7 @@ test("4. unrelated truncation message → no match in either mode (rejected from
 // --- Mode B ---
 
 test("4a. sentinel + trailing text → Mode B match, body NOT mutated, prefix_64 only in dump", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -182,7 +200,7 @@ test("4a. sentinel + trailing text → Mode B match, body NOT mutated, prefix_64
 
 test("4b. long trailing → prefix_64 captures only first 64 chars, byte_length reports full size", async () => {
   const long = SENTINEL_TS + " " + "x".repeat(200);
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -201,7 +219,7 @@ test("4b. long trailing → prefix_64 captures only first 64 chars, byte_length
 });
 
 test("4c. CACHE_FIX_MICROCOMPACT_REDACT_LEN=0 → prefix_64 absent", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -237,7 +255,7 @@ test("5a. CACHE_FIX_MICROCOMPACT_SENTINEL_PATTERN_1 adds custom Mode A pattern",
 });
 
 test("5b. custom Mode A regex + custom Mode B prefix → exact match goes to exact_matches", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   // Exact match against a custom regex from a sentinel family that does NOT
   // share the built-in prefix. Verifies exact-match path for custom families.
@@ -269,7 +287,7 @@ test("5c. custom Mode B prefix → variant-of-custom-family captured redacted in
   // EXACTLY normalizes, but its prefix-only variant must also be captured
   // in Mode B (redacted) — not silently dropped just because the variant
   // doesn't share the built-in `[Old tool result content cleared` prefix.
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const text = "[CC microcompact rev2 at 2026-04-30T17:00:00Z] (with trailing content)";
   const body = makeBody([
@@ -352,7 +370,7 @@ test("8. mixed array (text + image) — only the text matches → image untouche
 // --- Diagnostic dump ---
 
 test("9. dump set + sentinel match → JSONL line; session_id is hashed (no plaintext)", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -373,7 +391,7 @@ test("9. dump set + sentinel match → JSONL line; session_id is hashed (no plai
 });
 
 test("10. dump unset → no fs activity", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -395,7 +413,7 @@ test("10. dump unset → no fs activity", async () => {
 });
 
 test("11. multiple matches in one request → ONE JSONL line with arrays split A/B", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -455,7 +473,7 @@ test("13. normalize on + custom canonical → matched sentinel becomes the custo
 });
 
 test("14. normalize disabled, dump enabled → matches recorded in dump but body NOT mutated", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -500,7 +518,7 @@ test("15. two requests with different timestamps → byte-identical bodies after
 // --- Activation ---
 
 test("16. both gates unset → extension fires but exits early; no telemetry, no mutation, no fs", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -526,7 +544,7 @@ test("16. both gates unset → extension fires but exits early; no telemetry, no
 });
 
 test("17. only diagnostic enabled → telemetry present, JSONL written, no mutation", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -548,7 +566,7 @@ test("17. only diagnostic enabled → telemetry present, JSONL written, no mutat
 });
 
 test("18. only normalize enabled → telemetry present, mutation happens, no JSONL", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -568,7 +586,7 @@ test("18. only normalize enabled → telemetry present, mutation happens, no JSO
 });
 
 test("19. both enabled → telemetry, mutation, AND JSONL all happen; raw text captured pre-normalization", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),
@@ -598,7 +616,7 @@ test("19. both enabled → telemetry, mutation, AND JSONL all happen; raw text c
 });
 
 test("19a. CACHE_FIX_DUMP_MICROCOMPACT_INCLUDE_NORMALIZED=1 → adds normalized_text alongside raw sentinel_text", async () => {
-  const dir = await mkdtemp(join(tmpdir(), "mc-"));
+  const dir = await mcTemp();
   const dumpPath = join(dir, "dump.jsonl");
   const body = makeBody([
     assistantMsg("t1"),