docs: organize workflow examples by pattern

[HYBJzzq]

Description

Workflow pattern examples currently share a flat directory, making individual patterns harder to discover. Move the ten existing pattern scripts into six directories: task chaining, fan-out/fan-in, human interaction, monitor, child workflow, and multi-app workflows.

Each directory has its own README with setup instructions, run commands, and expected output. The main workflow README links to these directories, and the example test working directories and existing references are updated to follow the moves. All ten relocated Python scripts are unchanged.

Issue reference

Fixes #853.

Verification

Validated on Windows with Python 3.13.9:

• uv run pytest -m "not e2e" ./tests --ignore=tests/integration --ignore=tests/examples: 2,072 passed; 41 e2e tests deselected.
• uv run pytest tests/examples/test_workflow.py -v -s: all five passed against Dapr Runtime 1.18.4, with local Placement, Scheduler, and an in-memory actor state store.
• The moved child workflow example completed and printed both parent and child workflow messages against the same runtime.
• uv run ruff check, uv run ruff format --check, and uv run mypy: passed.
• Compared each relocated script against its original Git blob: all ten are identical. Checked the new README links.

Checklist

• Code compiles correctly
• Created/updated tests
• Extended the documentation

AI assistance

OpenAI Codex assisted with the directory reorganization, documentation updates, local validation, and preparation of this description.