* 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.
