fix(niri): conflict-free example keybinds and a niri-aware inject probe (#47)

The niri example binds move to Mod+Shift+M (toggle), Mod+Shift+S (start) and Mod+Shift+X (stop), free in stock niri and in Dank Material Shell's binds. inject-probe reuses the injector's niri guard, so it no longer reports the portal on niri.

Fixes #45
Fixes #46

scripts/measure_perf_baseline.py

@@ -433,8 +433,11 @@ def cmd_inject_probe(args: argparse.Namespace) -> int:
 
     Never emits keystrokes: end-to-end key-to-screen latency would type
     into the live desktop, so it stays a hardware-checklist item (#32).
+
+    On niri the portal is skipped with the injector's own niri guard: the
+    injector never offers the portal there, so the report must not claim it.
     """
-    from vocalinux.text_injection.text_injector import TextInjector
+    from vocalinux.text_injection.text_injector import TextInjector, _is_niri_session
 
     probe_text = "the quick brown fox jumps over the lazy dog 0123456789"
     started = time.monotonic()
@@ -462,16 +465,20 @@ def cmd_inject_probe(args: argparse.Namespace) -> int:
                     env=host_env(),
                 )
                 wtype_roundtrips.append(time.monotonic() - begin)
-    try:
-        from vocalinux.text_injection.remote_desktop_portal import RemoteDesktopPortal
+    portal_available = False
+    portal_seconds = None
+    portal_skip_reason = "niri" if _is_niri_session() else None
+    if portal_skip_reason is None:
+        try:
+            from vocalinux.text_injection.remote_desktop_portal import RemoteDesktopPortal
 
-        portal_started = time.monotonic()
-        portal_available = RemoteDesktopPortal().probe()
-        portal_seconds = time.monotonic() - portal_started
-    except Exception as exc:  # noqa: BLE001 - probe must never fail the pass
-        portal_available = False
-        portal_seconds = None
-        print(f"portal probe raised: {exc}", file=sys.stderr)
+            portal_started = time.monotonic()
+            portal_available = RemoteDesktopPortal().probe()
+            portal_seconds = time.monotonic() - portal_started
+        except Exception as exc:  # noqa: BLE001 - probe must never fail the pass
+            portal_available = False
+            portal_seconds = None
+            print(f"portal probe raised: {exc}", file=sys.stderr)
     print(
         json.dumps(
             {
@@ -481,6 +488,7 @@ def cmd_inject_probe(args: argparse.Namespace) -> int:
                 "wtype_empty_roundtrip_stats": describe(wtype_roundtrips),
                 "portal_available": portal_available,
                 "portal_probe_seconds": portal_seconds,
+                "portal_skip_reason": portal_skip_reason,
             },
             indent=2,
             sort_keys=True,