feat(tools): #467 lazygit opt-in installer

[primetimetank21]

feat(tools): #467 lazygit opt-in installer

Closes #467

Files Added / Modified

File	Change
scripts/linux/tools/lazygit.sh	New installer: tarball primary (no apt), macOS brew
scripts/windows/tools/lazygit.ps1	New installer: winget (JesseDuffield.lazygit), scoop fallback
scripts/windows/setup.ps1	Wire lazygit into ToolRegistry (NOT DefaultTools)
.tool-versions	Pin lazygit 0.63.0
tests/fixtures/stub-tools/{linux,windows}/lazygit.{sh,ps1}	Test stubs
tests/test_lazygit_installer.sh	Parity test (bash)
tests/test_lazygit_installer_pwsh.ps1	Parity test (PowerShell)

Opt-in Wiring

lazygit is NOT added to DEFAULT_TOOLS (Linux) or $DefaultTools (Windows).
Linux: directory auto-discovery. Windows: explicit $ToolRegistry entry only.
Selectable via --only=lazygit (Linux/macOS) or -Only 'lazygit' (Windows).

Version Pinned

lazygit 0.63.0 -- verified latest stable from
https://api.github.com/repos/jesseduffield/lazygit/releases/latest
(published 2026-07-04).

Linux asset naming confirmed (lowercase, no leading v):

• lazygit_0.63.0_linux_x86_64.tar.gz
• lazygit_0.63.0_linux_arm64.tar.gz

Binary at archive root (no subdirectory). macOS: brew install lazygit.

No git config applied -- lazygit works out of the box with no global config changes.

Tests (TDD -- RED then GREEN)

RED (pre-implementation):

• T_lazygit_in_list FAIL (lazygit.ps1 not registered in ToolRegistry)
• T_lazygit_version_pin FAIL (not in .tool-versions yet)
• T_lazygit_not_default PASS (correctly opt-in even before implementation)
• T_lazygit_optin_stub PASS (stub-dir dynamic registry picks up new stub)

GREEN (post-implementation):

• PowerShell suite: 4/4 PASS (run locally, confirmed)
• Bash suite: RED confirmed by code-analysis (no WSL on this Windows machine);
  tests cover discovery, not-default, version-pin, and stub opt-in.
  shellcheck: CLEAN on all new .sh files.

Existing test_setup_flags_pwsh.ps1: 36/36 PASS (no regressions).
PSScriptAnalyzer (lazygit.ps1): 0 issues.
PSScriptAnalyzer (CI paths setup.ps1 x2): 0 issues.

Pattern Used

Follows the proven opt-in tool pattern from delta (#466, PR #501).
Skill: .squad/skills/dev-setup-optin-tool/SKILL.md.

Key differences from delta:

• Tarball-primary (no apt-first) because Ubuntu PPA lags significantly.
• No git config step (lazygit works out of the box).
• No Set-*GitConfig / apply_*_git_config function needed.