Give a Mac an installer, an app bundle and a menu bar icon it can see

The macOS backends were already here: CoreAudio capture through ffmpeg,
pbcopy and CoreGraphics, Carbon hotkeys, the paths under ~/Library. What
was missing was everything that installs them, so install.sh hands over to
install-mac.sh on Darwin rather than growing a branch per line: the XDG
directories, the .desktop files and the shortcut registry mean nothing
there, and an application is a bundle rather than a path. The bundle
carries a copy of the interpreter, because macOS files the microphone and
Accessibility permissions against the process that asks, and a launcher
running Homebrew's python3 would have asked as python3 and shared the
grant with everything else on that interpreter. It is signed ad-hoc so a
reinstall is the same application rather than two more dialogs, and it
says so plainly when a brew upgrade has moved the tree it needs.
uninstall.sh and update.sh follow it.

The tray icon was invisible: QIcon.fromTheme wants a freedesktop icon
theme and hands back a null icon without one, which in a menu bar is the
whole interface gone. trayicon.py draws the three shapes as template
images, so they follow the menu bar into dark mode, and the bundle's icon
comes off the same glyph rather than a binary in the repository. Linux
keeps its own icons; these are used only where the theme has nothing.

paths.py is the fix that was never about a Mac. config.py imports ggml.py,
so ggml.py could not ask it where the data goes; each worked it out for
itself and only one of them knew about macOS. Settings went to ~/Library
while several gigabytes of models went to ~/.local/share, which is not a
place a Mac user looks and not a place uninstall.sh --purge would have
deleted from.

Ctrl+Space is the input-source switch there and Cmd+Space is Spotlight, so
the default is Ctrl+Option+Space, and hotkey.default_combo is the one
place that difference lives. The first paste asks for Accessibility with
kAXTrustedCheckOptionPrompt, which is what creates the row to switch on;
asking the other way opens a pane Dikte is not listed in. `dikte shortcut
status` asks the running instance, since the combination is held by that
process and by nothing else.

Local speech to text is the one piece a Mac builds by hand. whisper.cpp
publishes no macOS binary and Homebrew's is configured with
WHISPER_BUILD_SERVER=OFF, so it installs whisper-cli and not the server
Dikte talks to; program_path already takes a whisper-server off the PATH
or out of Settings, so the answer is the one a Linux distribution gets,
and the README carries the cmake line. CI grows a macOS job on 3.11 and
3.13, the only place the Carbon and CoreGraphics libraries have to be
there to be opened.

Written and tested on macOS 27.0 arm64. Two things are still unverified on
a Mac: the paste end to end, which waits on the Accessibility toggle, and
a meeting recording, which needs a loopback driver.

config.py

@@ -4,34 +4,21 @@ import collections
 import hashlib
 import json
 import os
-import pathlib
 import sys
 
 import api
 import ggml
 import i18n
 import paste
+import paths
 from i18n import t
 
 
-def _xdg(var, default):
-    return pathlib.Path(os.environ.get(var) or os.path.expanduser(default))
+_MACOS = sys.platform == "darwin"
 
-
-def _directories(platform=None):
-    """(settings, data), in the two places this system keeps them.
-
-    macOS keeps both in the one directory a Mac user's backup already knows
-    about. Everywhere else they are separate and follow the XDG variables.
-    """
-    if (platform or sys.platform) == "darwin":
-        support = pathlib.Path.home() / "Library/Application Support/Dikte"
-        return support, support
-    return (_xdg("XDG_CONFIG_HOME", "~/.config") / "dikte",
-            _xdg("XDG_DATA_HOME", "~/.local/share") / "dikte")
-
-
-CONFIG_DIR, DATA_DIR = _directories()
+# In paths.py rather than here, because ggml.py needs the same answer and
+# cannot ask this module: the import already runs the other way.
+CONFIG_DIR, DATA_DIR = paths.CONFIG_DIR, paths.DATA_DIR
 CONFIG_FILE = CONFIG_DIR / "config.json"
 HISTORY_FILE = DATA_DIR / "history.jsonl"
 RECORDINGS_DIR = DATA_DIR / "recordings"
@@ -438,11 +425,16 @@ DEFAULTS = {
     "speech_margin_db": 10.0,     # how far speech must rise above the noise floor
     "min_voiced_seconds": 0.3,
     "filter_hallucinations": True,
-    "shortcut": "Ctrl+Space",
+    # Ctrl+Space everywhere except a Mac, where macOS itself holds it for the
+    # input-source switch and Cmd+Space for Spotlight: neither is ours to take,
+    # so there Dikte starts on a combination a stock system leaves free.
+    "shortcut": "Ctrl+Option+Space" if _MACOS else "Ctrl+Space",
     # Ctrl+Alt+Space rather than Escape: the combination the recording started
     # with, one modifier along. Escape belongs to whatever window has focus, and
-    # while you are dictating something else usually has it.
-    "cancel_shortcut": "Ctrl+Alt+Space",
+    # while you are dictating something else usually has it. On a Mac that same
+    # trick lands on the toggle, Alt and Option being one key, so discarding
+    # gets a letter instead.
+    "cancel_shortcut": "Ctrl+Option+D" if _MACOS else "Ctrl+Alt+Space",
     "evdev_hotkey": False,
     "overlay_corner": "bottom-left",
     "keep_audio": False,