Add pre-commit hooks (ruff, vale) and fix lint errors

Add .pre-commit-config.yaml with ruff, pre-commit-hooks, and Vale.
Fix all prose lint errors in documentation: one sentence per line,
e.g./i.e. replaced with plain English, auto-hyphen compounds joined,
dashes normalized. Apply ruff auto-fixes to tests and benchmarks
(import sorting, formatting, f-strings, unused variables).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jensens

.pre-commit-config.yaml

@@ -0,0 +1,29 @@
+repos:
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.15.0
+    hooks:
+      - id: ruff
+        args: [--fix]
+        exclude: ^benchmarks/
+      - id: ruff-format
+        exclude: ^benchmarks/
+
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v5.0.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-yaml
+      - id: check-added-large-files
+
+  - repo: https://github.com/errata-ai/vale
+    rev: v3.9.6
+    hooks:
+      - id: vale
+        name: vale sync
+        pass_filenames: false
+        args: [--config=docs/.vale.ini, sync]
+        files: ^docs/sources/.*\.md$
+      - id: vale
+        args: [--config=docs/.vale.ini, --output=line, --minAlertLevel=error]
+        files: ^docs/sources/.*\.md$