test: split grind_lint.lean into 7 smaller files for faster CI

Split the single grind_lint.lean test (50+ seconds) into 7 separate files
that each run in under 7 seconds:

- grind_lint_list.lean (5.7s): List namespace with exceptions
- grind_lint_array.lean (4.6s): Array namespace
- grind_lint_bitvec.lean (3.9s): BitVec namespace with exceptions
- grind_lint_std_hashmap.lean (6.8s): Std hash map/set namespaces
- grind_lint_std_treemap.lean (~6s): Std tree map/set namespaces
- grind_lint_std_misc.lean (~5s): Std.Do, Std.Range, Std.Tactic
- grind_lint_misc.lean (5.5s): All other non-Lean namespaces

Total time: ~38 seconds (vs 50+ for original)

Each file maintains complete namespace coverage and preserves all existing
exceptions. The split enables better CI parallelization and faster feedback.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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