rename: cloud sync -> instance sync; cloud -> Timemachine Network; drop Tk

Product / UI / CLI / docs rebrand. Internal package, repo, and
on-disk dir names stay 'cloud_sync' / 'cloud-sync' / '.cloud-sync/'
to avoid breaking existing installs; a future commit can do the
file-system rename when the cost is worth paying.

User-facing changes:
  CLI prog name:        cloud-sync     -> instance-sync
  CLI description:      cloud-svc URL  -> Timemachine Network endpoint
  Dialog title:         CLOUD SYNC     -> INSTANCE SYNC
  Dialog title:         CLOUD CONFLICT -> INSTANCE CONFLICT
  Dialog title:         CONNECT CLOUD SAVE -> CONNECT TO THE NETWORK
  Card label:           Cloud Save     -> Remote Save
  Skip button:          Skip cloud sync -> Skip instance sync
  Body copy:            'the cloud'    -> 'the Timemachine Network'
  Window titles:        Cloud sync — ... -> Instance sync — ...
  Log prefix:           cloud-sync:    -> instance-sync:
  Error prose:          'cloud-sync token' -> 'instance-sync token'

Backend changes:
  restic --host tag:    cloud-sync     -> instance-sync
  State.host_tag dflt:  cloud-sync     -> instance-sync
  (Existing snapshots with the old tag still pull fine; we use 'latest'.)

Drop tkinter fallback: ui.py now offers Qt OR Headless. tkinter is
unnecessary given we already maintain Qt + headless; one less code
path to keep styled, smaller pyz. make_progress() picks Qt first,
falls through to HeadlessProgress on ImportError with a stderr hint
to 'pip install PySide6'.

README: rebrand title + prose; note repo/dir rename deferred; call
out the PySide6 install step. Conflict/login dialogs are now Qt-only;
without Qt, conflict aborts (defensive) and login tells the user to
paste the token manually.

52 tests green; no test-file label changes needed since they only
exercise internal APIs.

README.md

@@ -1,6 +1,8 @@
-# cloud-sync
+# instance-sync
 
-Per-user Minecraft state sync via [restic](https://restic.net). Single Python zipapp drops into Prism / MMC / ATLauncher pre-launch and post-exit hooks alongside [packwiz-installer-bootstrap](https://github.com/packwiz/packwiz-installer-bootstrap). Part of the [automc](https://git.timemachine.center/Timemachine/automc) platform.
+Per-user Minecraft instance sync over the **Timemachine Network**, backed by [restic](https://restic.net). Single Python zipapp drops into Prism / MMC / ATLauncher pre-launch and post-exit hooks alongside [packwiz-installer-bootstrap](https://github.com/packwiz/packwiz-installer-bootstrap). Part of the [automc](https://git.timemachine.center/Timemachine/automc) platform.
+
+> Repo + package + on-disk dir names are still `cloud-sync` / `cloud_sync` / `.cloud-sync/` for now — the rename was at the product / UI / CLI level. A future commit can pick up the file-system rename when it's worth breaking existing installs.
 
 See [`DESIGN.md`](DESIGN.md) for the full architecture (restic backend, two-port cloud-svc control plane, etc.).
 
@@ -32,18 +34,20 @@ Post-exit:
   python /path/to/cloud-sync.pyz push --url=https://cloud.tm.center --pack-folder=$INST_MC_DIR
 ```
 
-Player needs Python 3.10+ on PATH. Token file (`<INST_MC_DIR>/.cloud-sync/token`) gets the `discord_id:password` credentials from their `/register` Discord DM.
+Player needs Python 3.10+ on PATH AND a Qt binding (`pip install PySide6`). The first pull on a fresh instance opens a "CONNECT TO THE NETWORK" dialog; the player pastes a token they got via `/cloud register` in Discord. The token lands at `<INST_MC_DIR>/.cloud-sync/token`.
+
+If `PySide6` / `PyQt6` is missing the pyz falls back to headless mode (status to stdout). The conflict + login dialogs do not have a headless mode — without Qt the conflict path aborts the launch defensively, and the login path tells the user to paste the token manually.
 
 ## CLI
 
 ```
 python cloud-sync.pyz {pull,push} \
-    --url URL              cloud-svc data plane URL (required)
+    --url URL              Timemachine Network endpoint (required)
     --pack-folder PATH     Minecraft instance directory (default: cwd)
     --token-file PATH      override default <pack-folder>/.cloud-sync/token
     --restic-binary PATH   skip auto-discovery
     --no-download          fail if no usable restic; don't fetch from upstream
-    -g, --no-gui           headless mode
+    -g, --no-gui           headless mode (no Qt windows)
 ```
 
 ## Programmatic API (for frazclient)
@@ -82,19 +86,19 @@ Auto-excluded from sync. Multiple MC instances = multiple `.cloud-sync/` dirs wi
 ## Why Python (not a JAR)
 
 1. **Antivirus.** Unsigned JARs that auto-download binaries + upload files are textbook Windows Defender false-positive triggers. Python invoked by code-signed `python.exe` mostly sidesteps that.
-2. **Future Qt UI.** PySide6 opens a path to a real Qt UI (matching Prism's look) if richer surfaces are wanted later. JVM Qt bindings are abandoned.
+2. **Qt UI.** PySide6 gives us a real native window with the Prism-dark Steam-style layout. JVM Qt bindings are abandoned.
 3. **frazclient already needs Python.** Inlining as an import is zero overhead; the same package serves Prism via the pyz.
 
-Cost: players using Prism must have Python 3.10+ installed. Most Linux/Mac systems already do; Windows users install once from the Microsoft Store or python.org.
+Cost: players using Prism must have Python 3.10+ AND Qt installed. Most Linux/Mac systems ship Python; Windows users install once from the Microsoft Store or python.org. Qt comes via `pip install PySide6`.
 
 ## Where the data lives
 
 | Component | Role | Repo |
 |---|---|---|
-| `cloud-sync` (this) | Player-side. Subprocess restic for pull/push. | `Timemachine/cloud-sync` |
+| `instance-sync` (this) | Player-side. Subprocesses restic for pull/push. Surfaces login + conflict + progress dialogs. | `Timemachine/cloud-sync` |
 | `cloud-svc` | Operator-side control plane (provisioning + admin). | `Timemachine/cloud-svc` |
-| `restic-rest-server` (existing) | Data plane. Player's restic hits it directly with their password. | upstream |
-| `discord-bot` | Calls cloud-svc on `/register` to provision a player's cloud account. | `Timemachine/discord-bot` |
+| `restic-rest-server` (existing) | Timemachine Network data plane. Player's restic hits it directly with their password. | upstream |
+| `discord-bot` | Calls cloud-svc on `/cloud register` to provision a player's Timemachine Network account. | `Timemachine/discord-bot` |
 
 ## License