Add macOS support and use the SDK's key names

[PyFlat-JR]

What does this PR do?

Adds macOS on Apple silicon as a second platform next to Windows, and moves to Macro Deck SDK 3.0.0-beta.17 so both platforms publish exactly the key names the combo editor stores.

macOS hook

• A Quartz event tap on its own CFRunLoop thread. With Accessibility it can swallow a suppressed combo's key; with only Input Monitoring it falls back to listen-only, so hotkeys still fire but the key also reaches the focused app.
• Granting or revoking either permission takes effect without a restart: without access it retries every 5 seconds, and it swaps between the active and the listen-only tap when Accessibility changes. Revoking Accessibility no longer freezes all input.
• Modifiers are read from each event's flags, so a modifier released while macOS hid the keys (a password field) never sticks.
• A missing permission shows a notification that says which one and where to turn it on. The Accessibility one only appears once a trigger actually asks for suppression.

Shared core

• KeyboardHook holds the platform-neutral half (held keys, combo detection, what a suppressed combo swallows) and picks the backend for the OS. The Windows WH_KEYBOARD_LL hook moved into Windows/ unchanged in behaviour.
• An OS without a backend only logs a warning, so the plugin never fails to start.

Key names from the SDK

• The plugin's own key tables are gone. Both hooks translate native codes with MacroDeck.Sdk.Input.NativeKeys (Macro-Deck#1289) and name them with KeyNames, following ADR 0104 from Macro-Deck#1287: letters follow the active layout, digits and punctuation the key position (Minus, IntlBackslash), plus NumpadEnter and NumLock.
• On Windows punctuation now goes by scan code, so the German ß key is Minus like in the recorder. On macOS letters go through the active input source, so the Z key on a German Mac is Z.
• Right-hand modifiers still publish Ctrl, Shift, Alt and Meta, because the editor never stores RightCtrl for event triggers.
• Suppression resolves the spelling a trigger was stored with (-, Esc, Cmd, ...) the same way the host's trigger matching does.

Build and release

• manifest.json gets an osx-arm64 entrypoint and the host:notifications permission, macrodeck-build.json a matching target, and CI also runs on macos-latest.
• All Macro Deck packages and the release workflow's cli-version are on 3.0.0-beta.17, the Store's current minimum.

Docs

• README has a macOS section (permissions, Cmd as Meta, password fields, keys macOS never reports). AGENTS.md describes the backends and the SDK key lookup.

Checklist

• I have read AGENTS.md.
• dotnet build and dotnet test pass locally (0 warnings, 63 tests).
• macrodeck-plugin test passes against the packed artifact (0 failed).
• I updated README.md / AGENTS.md where this changes what they describe.

Tested on

• Windows 11: hotkeys, suppression, punctuation on a German layout.
• macOS on Apple silicon with a German input source: permission prompts and notifications, granting and revoking Accessibility while running, letters following the input source, ß as Minus, right-hand modifiers, suppression of Ctrl+ß.