feat: add reusable GitHub Release binary installer framework

[endavis]

Problem

Projects frequently need to install CLI tools distributed as GitHub Release binaries (e.g., age, sops, just, delta). Each project writes its own download/extract logic.

Proposed Solution

Add an optional tools/doit/install_tools.py module with reusable helpers:

• get_latest_github_release(repo) — fetch latest release tag from GitHub API (supports GITHUB_TOKEN auth)
• get_install_dir() — cross-platform install directory (~/.local/bin on Linux/macOS, %USERPROFILE%\.local\bin on Windows)
• Platform-specific download/extract logic (Linux tarball, macOS brew, Windows zip)
• A task_install_* pattern for defining installable tools

This pattern was developed in pynetappfoundry (tools/doit/install_tools.py) for installing age and sops, but the framework is fully generic. Needs utilities extracted as public functions and tool-specific config parameterized.

[endavis]

Implementation Plan for #293: feat: add reusable GitHub Release binary installer framework

Context

Projects frequently need to install CLI tools distributed as GitHub Release binaries. The existing tools/doit/install.py already has _get_latest_github_release() and _install_direnv() with basic platform detection. The issue wants to generalize this into a reusable framework so downstream projects can easily add new tool installers.

Overview

Create a new tools/doit/install_tools.py module with public helper functions extracted and generalized from the existing install.py patterns. The existing _get_latest_github_release() in install.py will be refactored to call the new public function.

Files to Create/Modify

• tools/doit/install_tools.py — New module with:
  • get_latest_github_release(repo: str) -> str — public version of existing helper
  • get_install_dir() -> Path — cross-platform install directory (~/.local/bin on Linux/macOS, %USERPROFILE%\.local\bin on Windows)
  • download_github_release_binary(repo: str, version: str, asset_pattern: str, dest_name: str) -> Path — download and install a binary from a GitHub release
  • install_tool(name: str, repo: str, asset_patterns: dict[str, str], version_cmd: list[str] | None = None) -> None — high-level installer that checks if tool exists, downloads if not
  • task_install_tool(name: str, repo: str, asset_patterns: dict[str, str], version_cmd: list[str] | None = None) -> dict[str, Any] — factory function to create doit task dicts for tool installation
• tools/doit/install.py — Refactor _get_latest_github_release() to import from install_tools and _install_direnv() to use the new framework
• tests/test_doit_install_tools.py — Tests for all public functions
• tests/test_doit_install.py — Update if imports change

Test Plan

• test_get_latest_github_release_builds_correct_url — verify URL construction and header handling
• test_get_latest_github_release_with_token — verify GITHUB_TOKEN auth header
• test_get_install_dir_linux — returns ~/.local/bin on Linux
• test_get_install_dir_windows — returns %USERPROFILE%\.local\bin on Windows
• test_get_install_dir_creates_directory — ensures dir is created
• test_download_github_release_binary — verify URL construction and file placement
• test_install_tool_skips_when_present — skips install if tool already on PATH
• test_install_tool_installs_when_missing — calls download when tool not found
• test_task_install_tool_returns_valid_doit_task — valid task dict structure
• test_task_install_tool_has_correct_title — task metadata

Documentation

• Update docs/development/tooling.md or equivalent if it exists, to document the install_tools framework
• ADR needed: no (this extends existing patterns, not an architectural change)

Validation

• doit check passes
• doit list shows framework is discoverable
• Existing task_install_direnv still works after refactor

[endavis]

Addressed in PR #325