Python: Fix prek runner duplication and add skills (#3791)

* Python: fix prek runner running fmt/lint in all packages on core change

When a core package file changed, run_tasks_in_changed_packages.py ran
fmt, lint, and pyright in ALL 22 packages (66 tasks). Only type-checking
tasks (pyright, mypy) need to propagate to all packages since type
changes in core affect downstream packages. File-local tasks (fmt, lint)
only need to run in packages with actual file changes.

This reduces a core-only change from 66 tasks to 24 tasks (2 local +
22 pyright).

Also adds no-commit-to-branch builtin hook to protect the main branch
from direct commits.

* Python: add agent skills extracted from AGENTS.md and coding standards

Add 5 skills to python/.github/skills/ following the Agent Skills format:
- python-development: coding standards, type annotations, docstrings, logging
- python-testing: test structure, fixtures, running tests, async mode
- python-code-quality: linting, formatting, type checking, prek hooks, CI
- python-package-management: monorepo structure, lazy loading, versioning
- python-samples: sample structure, PEP 723, documentation guidelines

* Python: deduplicate AGENTS.md and instructions with agent skills

* updated skills

* fixes from review

* Python: increase timeout for web search integration test

python/.github/skills/python-code-quality/SKILL.md

@@ -0,0 +1,85 @@
+---
+name: python-code-quality
+description: >
+  Code quality checks, linting, formatting, and type checking commands for the
+  Agent Framework Python codebase. Use this when running checks, fixing lint
+  errors, or troubleshooting CI failures.
+---
+
+# Python Code Quality
+
+## Quick Commands
+
+All commands run from the `python/` directory:
+
+```bash
+# Format code (ruff format, parallel across packages)
+uv run poe fmt
+
+# Lint and auto-fix (ruff check, parallel across packages)
+uv run poe lint
+
+# Type checking
+uv run poe pyright       # Pyright (parallel across packages)
+uv run poe mypy          # MyPy (parallel across packages)
+uv run poe typing        # Both pyright and mypy
+
+# All package-level checks in parallel (fmt + lint + pyright + mypy)
+uv run poe check-packages
+
+# Full check (packages + samples + tests + markdown)
+uv run poe check
+
+# Samples only
+uv run poe samples-lint     # Ruff lint on samples/
+uv run poe samples-syntax   # Pyright syntax check on samples/
+
+# Markdown code blocks
+uv run poe markdown-code-lint
+```
+
+## Pre-commit Hooks (prek)
+
+Prek hooks run automatically on commit. They check only changed files and run
+package-level checks in parallel for affected packages only.
+
+```bash
+# Install hooks
+uv run poe prek-install
+
+# Run all hooks manually
+uv run prek run -a
+
+# Run on last commit
+uv run prek run --last-commit
+```
+
+When core package changes, type-checking (mypy, pyright) runs across all packages
+since type changes propagate. Format and lint only run in changed packages.
+
+## Ruff Configuration
+
+- Line length: 120
+- Target: Python 3.10+
+- Auto-fix enabled
+- Rules: ASYNC, B, CPY, D, E, ERA, F, FIX, I, INP, ISC, Q, RET, RSE, RUF, SIM, T20, TD, W, T100, S
+- Scripts directory is excluded from checks
+
+## Pyright Configuration
+
+- Strict mode enabled
+- Excludes: tests, .venv, packages/devui/frontend
+
+## Parallel Execution
+
+The task runner (`scripts/task_runner.py`) executes the cross-product of
+(package × task) in parallel using ThreadPoolExecutor. Single items run
+in-process with streaming output.
+
+## CI Workflow
+
+CI splits into 4 parallel jobs:
+1. **Pre-commit hooks** — lightweight hooks (SKIP=poe-check)
+2. **Package checks** — fmt/lint/pyright via check-packages
+3. **Samples & markdown** — samples-lint, samples-syntax, markdown-code-lint
+4. **Mypy** — change-detected mypy checks