🏷️ types: move to ty

[Copilot]

• Inspect the repo, referenced ty migration PRs, and current lint/typecheck setup
• Replace pyright with ty in project config, editor recommendations, and docs
• Update code/tests for ty compatibility and refresh the lockfile
• Run local lint, tests, and build validation to ensure CI passes
• Run final review/security validation and prepare the PR

[Copilot]

Pull request overview

This PR migrates the project’s Python type-checking workflow from pyright to ty, updating dev dependencies and developer tooling to keep lint/typecheck in sync with the new checker.

Changes:

• Replace pyright with ty in dev dependencies (pyproject.toml) and lockfile (uv.lock).
• Update lint commands/documentation to run ty check (Justfile + README).
• Remove pyright-specific ignore comments in tests and adjust a local variable annotation for type-checker compatibility.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
uv.lock	Removes pyright/nodeenv and adds locked ty distribution metadata.
pyproject.toml	Swaps dev dependency from pyright to ty, removes [tool.pyright], and tightens Ruff by no longer ignoring F401/F841.
justfile	Updates lint target to run ty check --error-on-warning before Ruff.
README.md	Updates development instructions to use ty instead of pyright.
.vscode/extensions.json	Updates VS Code extension recommendations to prefer the ty extension over Pylance.
tests/test_cli.py	Removes pyright private-usage ignore comments.
src/gh_llm/pr_body.py	Adds an explicit type annotation for blocks.

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[Copilot]

You removed the Pylance extension recommendation, but the repo’s VS Code settings still use python.analysis.* inlay hint settings (provided by Pylance). Either keep recommending ms-python.vscode-pylance, or update/remove those settings (and document the ty extension configuration) so the recommended extension set matches the workspace settings.

Suggested change

	"ms-python.python",
	"ms-python.python",
	"ms-python.vscode-pylance",