chore: switch to ruff + pydoclint, deprecate .gitingest, and perform a repo-wide quality sweep (#329)

* **Pre-commit**: replace `black` & `darglint` with `ruff-check` / `ruff-format`;
  add `pydoclint` for docstring quality
* **Deps**: drop `tomli`; tighten `typing_extensions`; add `eval-type-backport`;
  remove `black`, `djlint`, `pylint` from `requirements-dev`
* **Ignore files**: deprecate TOML-based `.gitingest`; introduce
  `.gitingestignore` (git-wildmatch, parsed via `_parse_ignore_file`)
* **Config**: new unified `[tool.ruff]` (lint + format + isort); delete
  `[tool.black]`, keep minimal `[tool.isort]` for now
* **Refactor/style**: adopt `from __future__ import annotations`, kw-only args,
  richer types; reorder params & `__all__`; move type-only imports under
  `if TYPE_CHECKING`; extract `_CLIArgs` `TypedDict`, migrate form data to
  `pydantic.QueryForm`; deduplicate `cli.main` / `_async_main`; use `pathlib`,
  avoid file-IO in async; replace magic numbers with constants; delete
  `is_text_file` (logic now lives in `FileSystemNode.content`)
* **Bug fix**: remove silent error in `notebook_utils._process_cell`
* **Docs**: refresh README badges
* **Tests**: update fixtures & assertions

**BREAKING**: new `.gitingestignore` file replaces (now-deprecated) `.gitingest`.

No functional API or CLI changes.

src/static/js/utils.js

@@ -150,12 +150,10 @@ function copyFullDigest() {
 
 // Add the logSliderToSize helper function
 function logSliderToSize(position) {
-    const minp = 0;
-    const maxp = 500;
-    const minv = Math.log(1);
-    const maxv = Math.log(102400);
+    const maxPosition = 500;
+    const maxValue = Math.log(102400); // 100 MB
 
-    const value = Math.exp(minv + (maxv - minv) * Math.pow(position / maxp, 1.5));
+    const value = Math.exp(maxValue * Math.pow(position / maxPosition, 1.5));
     return Math.round(value);
 }