[WIP]feat: add cross-platform installer scripts and binary release pipeline

[adeptofvoltron]

Summary

• Adds install/install.sh (Mac/Linux) and install/install.ps1 (Windows) for a single-command install with no Python prerequisite on the user's machine
• Adds .github/workflows/release.yml — 4-platform matrix build (linux-x64, darwin-x64, darwin-arm64, windows-x64) that compiles standalone PyInstaller binaries, runs a smoke test, generates SHA256 checksums, and publishes all 8 artifacts to GitHub Releases on every v* tag push
• Adds nimble/__main__.py as the PyInstaller entry point (also enables python -m nimble)

Install experience

Mac/Linux:

curl -fsSL https://raw.githubusercontent.com/adeptofvoltron/nimble/main/install/install.sh | sh

Windows (PowerShell):

powershell -c "iwr https://raw.githubusercontent.com/adeptofvoltron/nimble/main/install/install.ps1 | iex"

Key design decisions

• PyInstaller + --collect-all pynput — pynput uses dynamic platform imports that static analysis misses; --collect-all bundles all backends
• macos-14 pinned (not macos-latest) — guarantees Apple Silicon runner without drift risk
• Writability check for sudo — detects need for elevated permissions regardless of install path, not just when path equals /usr/local/bin
• Target validation in install.sh — Linux ARM64 users get a clear "not yet supported" message instead of a silent download failure

Test plan

• Push a v0.0.1-test tag and verify all 4 matrix jobs pass and GitHub Releases shows 8 assets (4 binaries + 4 checksums)
• Run smoke test: curl ... | sh on a fresh Mac (Intel and Apple Silicon) and Linux VM — confirm nimble --help works in a new terminal
• Run powershell -c "iwr ... | iex" on Windows 10/11 — confirm nimble --help works in a new terminal
• Test NIMBLE_INSTALL_DIR=~/.local/bin curl ... | sh — confirm no sudo prompt and binary in correct location
• Simulate SHA256 mismatch — confirm human-readable error and no partial binary left behind
• Test on WSL2 — confirm "Detected WSL" message appears and linux-x64 binary is used

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