fix(hygiene): .prettierignore must exclude Python build/test artifacts

Prettier had no excludes for venv/__pycache__/.mypy_cache/.pytest_cache/htmlcov,
so any local Python virtualenv in the tree drops thousands of third-party files
into `pnpm format:check` and makes the gate unpassable in a working checkout
(observed: ~2400 files from an untracked apps/coordinator venv).

Same category as the existing node_modules/dist/.next entries. This narrows what
the gate SCANS (generated trees), never what it ENFORCES over source.

Found while making the three gates pass honestly for the remediation mission's
TASK-0, rather than reaching for --no-verify.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

.prettierignore

@@ -4,6 +4,14 @@ pnpm-lock.yaml
 **/node_modules
 **/drizzle
 **/.next
+# Python build/test artifacts — same category as node_modules/dist/.next above.
+# Prettier must never scan generated trees; without these a local venv poisons
+# `pnpm format:check` with thousands of third-party files.
+**/venv
+**/__pycache__
+**/.mypy_cache
+**/.pytest_cache
+**/htmlcov
 .claude/
 docs/tess/TASKS.md
 docs/scratchpads/