feat(lessons): a lesson is yours to keep current too (#4195)

The lesson kind shipped with every mechanism for growing and nothing
telling a session to use them. `learned_from` is a list on purpose, the
dedup gate hands back an existing id rather than minting a twin, and
`update_lesson` already names re-keying a bad trigger as the edit that
pays most. None of that was reachable as a habit.

The exclusivity claim was the bug. The skill said "a preference is the
one record you keep current yourself", and by naming only preferences it
put lessons outside the habit. That sentence is now "a preference is
yours to keep current", which says the same thing about preferences
without saying anything false about lessons.

Beside it, a paragraph on what growing a lesson means: another incident
added to what taught it, a claim stated more exactly, or a trigger
re-keyed to the situation that really fired. Written as a practice
rather than a prohibition (rule 165) — the reader is named as the one
person placed to judge the trigger, because they are standing in the
situation it claims to name.

`get_lesson` carries the same prompt at the moment it bites: a session
reading a lesson inside the situation it names is the only reader who
can tell whether the trigger is keyed to what actually fired.

The guidance-ownership registry gains the topic and re-points the
preference topic's statement, since the phrase it pinned is the sentence
this change rewrites — the module asks for exactly that, in the same
commit. No index marker: the index names session-start reflexes and this
one fires mid-work, so `_INSTRUCTIONS` stays at 1998/2000.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

tests/test_guidance_ownership.py

@@ -118,7 +118,8 @@ TOPICS: tuple[Topic, ...] = (
           "an empty session is not evidence of an empty rulebook",
           index=('content_type="rule"', "nothing matched")),
     Topic("rules bind, preferences guide and are kept current", U, ("preference", "update_preference"),
-          "a preference is the one record you keep current yourself", index=("preferences guide",)),
+          "updating one mid-work is the normal case rather than an interruption of it",
+          index=("preferences guide",)),
     Topic("kind is force: a rule binds, a preference guides, a lesson informs", U,
           ("lesson", "costs time", "costs consistency"),
           "what happens if someone doesn't do this",
@@ -129,6 +130,14 @@ TOPICS: tuple[Topic, ...] = (
           # mis-routing #3733 recorded happens, and the caller there has not
           # necessarily read the skill.
           shared_with=("docstrings",)),
+    Topic("a lesson grows each time it proves itself", U,
+          ("update_lesson", "re-keyed", "grows each time"),
+          "one claim that has met the same failure four times is worth more "
+          "than four claims that each met it once",
+          # No index marker. The index names session-START reflexes, and this
+          # one fires mid-work, the moment a lesson arrives in a situation it
+          # actually names. `lessons inform` already points at the kind.
+          shared_with=("docstrings",)),
     Topic("preferences shape how work is done, never what is recorded", U,
           ("never what gets recorded",),
           "a preference never makes a task into a note"),