fix(lessons): a lesson's name is one claim on one line (#4797)

#4797 "A lesson's what takes a whole narrative, and the narrative becomes
its name". `what` is the title every listing and menu prints. Nothing
enforced its documented "one line", so lessons written with the incident
in `what` printed up to ~1,500 characters as a menu line, buried the
claim, and diluted the trigger in the embedded title. That was 14 of the
39 lessons on this install.

- lessons.require_claim refuses a `what` over WHAT_MAX_CHARS (240) or
  running over several lines. The refusal says the story goes in
  `insight`.
- Both doors call it before writing:
  - MCP create_lesson / update_lesson;
  - REST create / update.
  An update checks only a NEW name, so a lesson stored with a long one can
  still take the edit that repairs it.
- lessons.claim_line is the display half. _menu_name shows an over-long
  stored name as its first sentence marked " …", because a door guard
  does not undo rows already stored and an unrepaired install would keep
  printing them.
- The tool docstrings state the bound.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_lesson_claim.py

@@ -0,0 +1,125 @@
+"""A lesson's name is one claim on one line (#4797).
+
+`what` is the title every listing and menu prints. Written as the incident
+instead of the claim, it turned a menu line into 1,416 characters with the
+claim somewhere in the middle. Two halves are pinned: the doors refuse a new
+one, and the menu shows one line for a name stored before they did.
+"""
+from __future__ import annotations
+
+import inspect
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, patch
+
+import pytest
+
+from scribe.mcp._context import _user_id_ctx
+from scribe.mcp.tools.lessons import create_lesson, update_lesson
+from scribe.services import lessons as lessons_svc
+from scribe.services.lessons import WHAT_MAX_CHARS, claim_line, require_claim
+
+TRIGGER = "an existing call is about to double as a liveness signal"
+CLAIM = ("A check-in piggybacked on an existing call inherits every backoff "
+         "that call is ever given")
+STORY = (
+    "The operator reported their agent showing offline while it ran. "
+    + "The lease poll backed off to 900s while the roster called 300s stopped. " * 6
+).strip()
+
+
+# ── The bound ──────────────────────────────────────────────────────────────
+
+def test_a_one_line_claim_passes():
+    require_claim(CLAIM)
+    require_claim("x" * WHAT_MAX_CHARS)
+
+
+@pytest.mark.parametrize("what", [
+    "x" * (WHAT_MAX_CHARS + 1),
+    "A claim.\n\nAnd then the story of how it was learned.",
+], ids=["over the bound", "several lines"])
+def test_a_story_in_the_name_is_refused_with_where_it_goes(what):
+    with pytest.raises(ValueError) as err:
+        require_claim(what)
+    message = str(err.value)
+    assert "Nothing was written" in message
+    assert "insight" in message, "the refusal must say where the story belongs"
+
+
+# ── The doors ──────────────────────────────────────────────────────────────
+
+@pytest.mark.asyncio
+async def test_the_mcp_create_refuses_before_writing():
+    _user_id_ctx.set(7)
+    created = AsyncMock()
+    with patch.object(lessons_svc, "create_lesson", created):
+        with pytest.raises(ValueError):
+            await create_lesson(what=STORY, when_to_apply=TRIGGER)
+    created.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_the_mcp_update_refuses_a_new_long_name():
+    _user_id_ctx.set(7)
+    updated = AsyncMock()
+    with patch.object(lessons_svc, "update_lesson", updated):
+        with pytest.raises(ValueError):
+            await update_lesson(lesson_id=1, what=STORY)
+    updated.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_a_lesson_stored_with_a_long_name_can_still_be_edited():
+    """Only a NEW name is checked. Refusing every edit of a lesson stored
+    before the bound would also refuse the edit that repairs it."""
+    _user_id_ctx.set(7)
+    note = SimpleNamespace(
+        id=1, title=STORY, body="b", tags=[], project_id=None,
+        note_type="lesson", data={"what": STORY}, arose_from_id=None,
+        created_at=None, updated_at=None,
+    )
+    updated = AsyncMock(return_value=note)
+    with patch.object(lessons_svc, "update_lesson", updated), \
+         patch("scribe.mcp.tools.lessons.systems_tools.attach_systems", AsyncMock()), \
+         patch("scribe.mcp.tools.lessons.lesson_rules_svc.attach_lesson_rules", AsyncMock()):
+        await update_lesson(lesson_id=1, when_to_apply=TRIGGER)
+    assert updated.await_args.kwargs["what"] is None
+
+
+@pytest.mark.parametrize("handler", ["create_lesson_route", "update_lesson_route"])
+def test_the_rest_door_refuses_too(handler):
+    """The web form writes lessons as well, and a bound one door enforces is
+    a bound the other door walks around."""
+    from scribe.routes import lessons as routes
+
+    src = inspect.getsource(getattr(routes, handler))
+    write = "lessons_svc." + handler.removesuffix("_route") + "("
+    assert "require_claim(" in src
+    assert src.index("require_claim(") < src.index(write), \
+        "the check runs after the write it exists to prevent"
+
+
+# ── The display ────────────────────────────────────────────────────────────
+
+def test_a_short_name_is_shown_as_it_is():
+    assert claim_line(CLAIM) == CLAIM
+
+
+def test_a_stored_story_shows_as_its_first_sentence_marked_cut():
+    line = claim_line(STORY)
+    assert line == "The operator reported their agent showing offline while it ran. …"
+    assert "\n" not in line
+
+
+def test_a_first_sentence_past_the_bound_is_cut_at_a_word():
+    line = claim_line("word " * 100)
+    assert line.endswith(" …")
+    assert len(line) <= WHAT_MAX_CHARS + 2
+
+
+def test_the_menu_names_a_long_lesson_in_one_line():
+    from scribe.services.plugin_context import _menu_name
+
+    name = _menu_name(STORY, "lesson", {"what": STORY, "when_to_apply": TRIGGER}, "")
+    assert name.endswith(" …")
+    assert len(name) <= WHAT_MAX_CHARS + 2