Delete upstream docs apparatus; rewrite README for the fork

The CDiT fork is single-household and was carrying an entire upstream
docs/ mkdocs site documenting features the fork has removed (sleep mode,
take-over-control, brightness_mode selector, YAML config). The README
mostly auto-generated from those pages via markdown-code-runner.

What's gone:

- docs/ — all 11 pages + assets + run_markdown_code_runner.py
- .github/workflows/docs.yml — zensical+shinylive GitHub Pages build
- .github/workflows/markdown-code-runner.yml — auto-edit of README from docs/
- .github/update-services.py / update-strings.py — would clobber the
  hand-edited services.yaml / strings.json
- scripts/update-generated-content — orchestrator for the above
- custom_components/adaptive_lighting/_docs_helpers.py + docs_gen.py —
  only used by the deleted markdown-code-runner
- zensical.toml — docs-site config
- "docs" dependency group in pyproject.toml (markdown-code-runner,
  shinylive, zensical, etc.) + lock regenerated

What's new:

- README.md rewritten to describe the fork's actual surface — 3 switches,
  4 number entities, 3 sensor entities per profile, 2 services (apply +
  change_switch_settings), entry-only setup, UI tuning, sun source.
  Preserves the existing "What's new in 2.1" / "2.2" block quotes.
- webapp/README.md annotated to flag the Shiny simulator models the
  upstream curve (with brightness_mode, sleep mode, etc.) and does not
  reflect the fork.
- CLAUDE.md command table no longer references update-generated-content.

Sensor.py + test_sensor_platform.py: incidental black reformat from the
lint pass (multi-arg function calls split per line).

Tests still pass (123/123). Lint clean. Sensors implementation
unchanged.

scripts/update-generated-content

@@ -1,11 +0,0 @@
-#!/usr/bin/env bash
-
-set -ex
-
-cd "$(dirname "$0")/.."
-
-uv sync --group docs
-uv pip install -e .
-uv run python docs/run_markdown_code_runner.py
-uv run python .github/update-services.py
-uv run python .github/update-strings.py