Add doctor diagnostics, install tooling, and ADF driver auto-resolution

[tbdye]

Summary

AmiFUSE currently requires users to manually install dependencies, diagnose missing components, and pass --driver flags for common ADF images. This PR adds a diagnostic/repair command (amifuse doctor) and platform-specific bootstrap scripts that get new users from zero to a working mount in one command. ADF floppy images now auto-resolve their filesystem handler without --driver.

What's New

amifuse doctor — standalone diagnostic command (extracted from fuse_fs.py into amifuse/doctor.py):

• Detects FUSE backend across all platforms (macFUSE/FUSE-T/osxfuse, fusermount/libfuse, WinFSP with version check)
• Tests machine68k in a subprocess so a segfault doesn't crash the doctor
• Checks shell registration and PATH reachability on Windows
• Color-coded human output by default, ASCII fallback on Windows cp1252 consoles
• --json flag for CI/scripting — structured CheckResult output per check

amifuse doctor --fix — auto-repairs what it can:

• Registers shell extensions, adds Scripts dir to user PATH (Windows, via HKCU registry)
• Prints actionable instructions for issues that need manual intervention (FUSE install, machine68k-amifuse fork)
• Never elevates privileges without user confirmation

Bootstrap scripts:

• tools/install-windows.ps1 — detects Python/WinFSP via winget (manual URL fallback), creates venv at %LOCALAPPDATA%\amifuse\venv, installs machine68k-amifuse fork, hands off to amifuse doctor --fix
• tools/install.sh — brew/apt/dnf detection, FUSE backend install, same venv strategy at ~/.local/share/amifuse/venv
• Both scripts auto-detect repo checkouts (via pyproject.toml presence) and use pip install -e . instead of PyPI

Bundled FastFileSystem handler — ADF floppy images don't embed a filesystem driver (unlike HDF hard disk images). The Commodore FastFileSystem handler (~28KB, freely distributable) is bundled in amifuse/drivers/ and handles all standard ADF DOS types (DOS0–DOS7: OFS, FFS, and their international/dir-cache variants). This eliminates the need for users to source and specify --driver manually when mounting floppies. The .gitignore is updated to scope handler exclusion patterns to the repo root (where make download places them) so the bundled copy is tracked.

README — new "Quick install (recommended)" section with bootstrap scripts as the primary path, "From source" section for developers, and "Diagnosing Issues" section with doctor examples.

How It Works

Doctor architecture: Each check returns a CheckResult dataclass carrying status, message, optional fix_fn (callable), and optional fix_description (human-readable repair instruction). This separates execution from display — the same results render as color-coded text or JSON depending on the flag.

FUSE detection split: detect_fuse_backend() returns a dict of discovered backends for diagnostic display. The existing check_fuse_available() remains the mount-time guard (raises SystemExit). They query the same things but serve different callers.

Venv strategy: Bootstrap scripts use the active venv if one is detected, otherwise create a dedicated venv. They never pass --break-system-packages.

WinFSP version check: Uses GetFileVersionInfoW + VerQueryValueW on winfsp-x64.dll to enforce >= 2.0.

machine68k on Windows: The PyPI machine68k package segfaults; both the bootstrap script and doctor explicitly install/check for the machine68k-amifuse fork.

Files Changed

Status	File	Description
New	amifuse/doctor.py	Doctor command, CheckResult, --fix, --json
New	amifuse/drivers/FastFileSystem	Bundled handler for ADF auto-resolution
New	tools/install-windows.ps1	Windows bootstrap script
New	tools/install.sh	macOS/Linux bootstrap script
New	tests/unit/test_doctor.py	66 tests for doctor checks, fix mode, JSON output
Modified	amifuse/fuse_fs.py	Doctor extraction, ADF auto-resolution, dynamic __version__
Modified	amifuse/platform.py	detect_fuse_backend(), driver resolution functions
Modified	pyproject.toml	package-data for bundled amifuse/drivers/*
Modified	README.md	Quick install, from-source, and diagnosing-issues sections
Modified	.gitignore	Scope handler patterns to repo root
Modified	tests/unit/test_cli_help.py	Doctor JSON schema assertions
Modified	tests/unit/test_fuse_fs.py	Updated for doctor extraction and ADF auto-resolution

Test Plan

Automated (all passing):

• 66 unit tests in test_doctor.py — all check types, --fix mode, JSON output serialization, edge cases (missing deps, partial installs, segfaulting machine68k)
• test_cli_help.py updated with doctor subcommand and JSON schema assertions
• test_fuse_fs.py updated for doctor delegation and ADF auto-resolution
• Full existing test suite remains green

Manual validation performed:

• Clean Windows slate -> install-windows.ps1 -> all doctor checks green
• WinFSP installed via winget with elevation prompt, venv created, editable install, machine68k-amifuse fork, doctor --fix registered shell extensions
• Partial install recovery: removed WinFSP, re-ran script, only WinFSP step executed
• doctor --json output validated with Python json.loads()
• ASCII fallback verified on Windows cp1252 console (Unicode symbols -> ASCII +/X)
• ADF mount without --driver flag using bundled FastFileSystem handler