Add ensure subcommand for resilient SessionStart hook

CLAUDE.md

@@ -20,7 +20,7 @@ dotnet publish src/Claudelk.Cli -c Release
 # hooks invoke. ~1.6s cold per command.
 ```
 
-CLI subcommands: `scan [--debug]`, `pair <id>`, `on`, `off`, `color <#RRGGBB>`, `blink <#RRGGBB> [pulses] [ms] [--end <#RRGGBB>]`, `brightness 0-100`, `speed 0-100`, `effect 0x80-0x9f`, `temp 0-100`. All commands accept `--device <id>` to override the saved default.
+CLI subcommands: `scan [--debug]`, `pair <id>`, `ensure [--color <#RRGGBB>]` (verify connection; reconnect/re-pair/power-on as needed, then set colour — default `#ffffff`; used by the `SessionStart` hook), `on`, `off`, `color <#RRGGBB>`, `blink <#RRGGBB> [pulses] [ms] [--end <#RRGGBB>]`, `brightness 0-100`, `speed 0-100`, `effect 0x80-0x9f`, `temp 0-100`. All commands accept `--device <id>` to override the saved default.
 
 ## Tests
 

README.md

@@ -64,6 +64,7 @@ claudelk scan              # add --debug to see all BLE adverts
 claudelk pair <device-id>
 
 # 3. Drive it.
+claudelk ensure                                # verify connection (re-pair / power-on if needed), then white
 claudelk on
 claudelk color "#ff8800"
 claudelk blink "#ff0000"                       # default 4×250ms, holds colour
@@ -98,11 +99,15 @@ waiting for your next message. Never turns off.
 | `Notification`     | `permission_prompt`  | red `#ff0000`, 5 s blink, ends on white      |
 | `Notification`     | `idle_prompt`        | yellow `#ffff00`, 3 s blink, ends on white   |
 
+`ensure` is used instead of plain `color` so a fallen-out Windows pairing or
+a powered-off strip is repaired on session start (reconnect → idempotent
+re-pair → power-on → set white).
+
 ```json
 "SessionStart": [{
   "hooks": [{
     "type": "command", "shell": "powershell", "async": true,
-    "command": "& 'C:\\path\\to\\claudelk.exe' color '#ffffff'"
+    "command": "& 'C:\\path\\to\\claudelk.exe' ensure"
   }]
 }],
 "Notification": [

src/Claudelk.Cli/Dispatcher.cs

@@ -20,6 +20,7 @@ public static async Task<int> RunAsync(string[] args)
             {
                 "scan" => await ScanAsync(args),
                 "pair" => await PairAsync(args),
+                "ensure" => await EnsureAsync(args),
                 "on" => await SimpleCommandAsync(args, d => d.TurnOnAsync()),
                 "off" => await SimpleCommandAsync(args, d => d.TurnOffAsync()),
                 "color" => await ColorAsync(args),
@@ -56,6 +57,8 @@ private static void PrintHelp()
             Commands:
               scan [--debug]             Discover nearby ELK-BLEDOM strips (--debug lists all BLE adverts)
               pair <device-id>           Save a device as the default target
+              ensure [--color <#RRGGBB>] Verify connection; reconnect/repair-pair/power-on if needed, then set colour
+                                         (default colour: #ffffff)
               on                         Power on the saved device
               off                        Power off the saved device
               color <#RRGGBB | R G B>    Set RGB color
@@ -146,6 +149,29 @@ private static async Task<int> PairAsync(string[] args)
         return 0;
     }
 
+    private static async Task<int> EnsureAsync(string[] args)
+    {
+        var colorHex = ExtractOption(args, "--color") ?? "#ffffff";
+        if (!TryParseHex(colorHex, out var r, out var g, out var b))
+        {
+            Console.Error.WriteLine("ensure: --color expects '#RRGGBB'.");
+            return 1;
+        }
+
+        using var device = await ResolveDeviceAsync(args);
+
+        // Restore the paired-list fast path if ConnectByIdAsync had to fall back
+        // to an advertisement scan. PairAsync is a no-op when already paired.
+        await device.PairWithWindowsAsync();
+
+        // Power on explicitly: this firmware silently drops SetColor writes that
+        // arrive while the strip is in the off state.
+        await device.TurnOnAsync();
+        await device.SetColorAsync(r, g, b);
+        Console.WriteLine($"Ensured {device.Name} ({device.Id}) on, colour #{r:X2}{g:X2}{b:X2}.");
+        return 0;
+    }
+
     private static async Task<int> SimpleCommandAsync(string[] args, Func<ElkBledomDevice, Task> action)
     {
         using var device = await ResolveDeviceAsync(args);