Speak of the LMS generically, not Canvas specifically

The tool targets any LTI 1.3 platform; Canvas is the primary target
but nothing outside the Canvas-specific custom variable substitutions
depends on it. User-facing strings and the README now say "LMS"
except where a mechanism genuinely is Canvas's (the $Canvas.* /
com.instructure.* substitutions and their handling), and the README
states plainly that the tool has so far been exercised only against
the saltire emulator, not yet a production LMS.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_report_ui.py

@@ -78,4 +78,4 @@ def test_pronouns_flow_to_pages(instructor):
     instructor.post("/dev/launch/dev-student-1")
     page = instructor.get("/me").get_data(as_text=True)
     assert "Ada Lovelace (she/her)" in page
-    assert "drawn from Canvas" in page
+    assert "drawn from your" in page