fix: skip __pycache__ dirs when merging namespace packages

[xangcastle]

When uv or the host Python compiles a shared namespace init.py to bytecode, the resulting .pyc files embed the absolute source path in their headers. Two packages sharing the same namespace therefore produce non-identical .pyc files, which triggered CollisionResolutionStrategy::Error in create_symlinks.

Python regenerates .pyc files on demand, so pycache directories can safely be omitted from the symlink forest. The fix skips any directory named pycache in create_symlinks.

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Changes are visible to end-users: no

Test plan

• New test cases added

[aspect-workflows]

✨ Aspect Workflows Tasks

📅 Thu Jun 11 04:04:47 UTC 2026

❌ 3 failed tasks

• ❌ buildifier · ⏱ 18.2s · 🐙 GitHub Actions · ☑️ Check
  💬 failed in diff · Format failed (1 file needs format)
• ❌ test (test-e2e-bazel-8) · ⏱ 26m 51s · 🐙 GitHub Actions · ☑️ Check
  💬 failed in test · Bazel test failed
• ❌ test (test-e2e-bazel-9) · ⏱ 1m 13s · 🐙 GitHub Actions · ☑️ Check
  💬 failed in test · Bazel test failed

✅ 4 successful tasks

• ✅ gazelle · ⏱ 21.1s · 🐙 GitHub Actions · ☑️ Check
  💬 Gazelle complete (clean)
• ✅ test (test-examples-uv_pip_compile-bazel-8) · ⏱ 26.2s · 🐙 GitHub Actions · ☑️ Check
  💬 Bazel test complete (1/1 passed · 1 cached)
• ✅ test (test-root-bazel-8) · ⏱ 36m 33s · 🐙 GitHub Actions · ☑️ Check
  💬 Bazel test complete (123/123 passed)
• ✅ test (test-root-bazel-9) · ⏱ 37m 10s · 🐙 GitHub Actions · ☑️ Check
  💬 Bazel test complete (122/122 passed)

🛠️ Fix

❌ buildifier (buildifier)

aspect buildifier --severity=info -- e2e/cases/pth-pycache-collision/BUILD.bazel

# without Aspect CLI
bazel run --run_in_cwd @buildifier_prebuilt//buildifier -- \
  e2e/cases/pth-pycache-collision/BUILD.bazel

_{Install aspect: docs.aspect.build/cli/install}

🔁 Reproduce

❌ buildifier (buildifier)

aspect buildifier --severity=fail --base-ref=origin/1.x

❌ test (test-e2e-bazel-8 · test-e2e-bazel-9)

aspect test -- //cases/pth-pycache-collision:test

# without Aspect CLI
bazel test -- //cases/pth-pycache-collision:test

_{Install aspect: docs.aspect.build/cli/install}

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