fix(sandbox): bind parent dir for globstar allow_write on bwrap (#321)

* fix(sandbox): bind parent dir for globstar allow_write on bwrap

Fine-grained per-path mounts under read-only project binds broke pip
install into in-project .venv directories. Always mount the parent tree
for ** write rules instead.

Fixes #315

* test(sandbox): tighten globstar bind assertions and ensure ~/.npm exists for e2e

Strengthen TestBubblewrapAllowWriteGlobstarBindsParentOnly to verify the
parent dir is writably bound and the child path is read-only bound, not
just substring presence. Pre-create ~/.npm in the e2e harness so
bubblewrap --bind-try does not skip the npm cache dir on fresh runners.

* switch pnpm to /tmp in sandbox e2e

* test(sandbox): update glob ** test for parent-bind semantics

Globstar allow_write now binds the parent dir only (e2e740d), so the
test should assert the parent is writably bound and child subdirs are
not individually bound, instead of substring-matching subdir names.

* fix(sandbox): bind correct base dir for in-pattern globstar allow_write

Globstar allow_write previously used extractGlobParentDir, which walks past
the first ** and yields the wrong root for patterns like /a/b/**/d/**/e.
Introduce extractGlobstarWriteBaseDir, which takes the prefix before the
first /**, and use it in processWriteRule. Also dedup the coarse-fallback
parent-bind loop to mirror the read-rule fallback.

test/pm-e2e.js

@@ -47,15 +47,37 @@ function cleanup(dir) {
   }
 }
 
+// npm-restrictive allow_write includes /tmp/**. Use cache/store paths under /tmp so
+// bubblewrap can bind /tmp read-write without pre-creating ~/.npm or ~/.cache/pnpm.
+function pmEnv(pm) {
+  const base = path.join(os.tmpdir(), 'pmg-e2e');
+  fs.mkdirSync(base, { recursive: true });
+
+  const env = { ...process.env };
+  env.npm_config_cache = path.join(base, 'npm-cache');
+  fs.mkdirSync(env.npm_config_cache, { recursive: true });
+
+  if (pm === 'pnpm') {
+    env.PNPM_HOME = path.join(base, 'pnpm-home');
+    env.npm_config_store_dir = path.join(base, 'pnpm-store');
+    fs.mkdirSync(env.PNPM_HOME, { recursive: true });
+    fs.mkdirSync(env.npm_config_store_dir, { recursive: true });
+    env.PATH = `${env.PNPM_HOME}${path.delimiter}${env.PATH}`;
+  }
+
+  return env;
+}
+
 function testPackageManager(pm) {
   const testDir = createTempDir(`pmg-e2e-${pm}-`);
+  const env = pmEnv(pm);
   console.log(`\n  Test directory: ${testDir}`);
 
   try {
     // Initialize project
     test(`${pm}: Initialize project`, () => {
       const initCmd = pm === 'npm' ? 'npm init -y' : 'pnpm init';
-      const result = exec(initCmd, { cwd: testDir });
+      const result = exec(initCmd, { cwd: testDir, env });
       if (!result.success) {
         console.log(`    ❌ FAIL: ${result.error}`);
         return false;
@@ -77,7 +99,7 @@ function testPackageManager(pm) {
       const addCmd = pm === 'npm'
         ? `npm install ${depsList}`
         : `pnpm add ${depsList}`;
-      const result = exec(addCmd, { cwd: testDir });
+      const result = exec(addCmd, { cwd: testDir, env });
       if (!result.success) {
         console.log(`    ❌ FAIL: ${result.error}`);
         return false;
@@ -122,7 +144,7 @@ function testPackageManager(pm) {
 
       // Reinstall
       const installCmd = pm === 'npm' ? 'npm install' : 'pnpm install';
-      const result = exec(installCmd, { cwd: testDir });
+      const result = exec(installCmd, { cwd: testDir, env });
       if (!result.success) {
         console.log(`    ❌ FAIL: ${result.error}`);
         return false;