feat(plugin): the seam that erases the evidence is where the unresolved rules get named (#4216)

Step 5 of milestone 419. The milestone's subject is that a rule read and
ignored is arithmetically identical to a rule read and followed, and the
compaction is where that identity becomes permanent — the turns holding the
evidence are summarised away, and the unjudged thing survives as nothing.

WHY THIS IS ASSEMBLED IN THE HOOK. `rule_usage_events` has no session column;
it is per user over a window. A session-scoped answer therefore cannot be
asked of the server, and has to be built where a session is a thing that
exists. Four ledgers four hooks already write:

  .rules.ids      an arm NAMED the rule
  .opened.ids     the session called get_rule      (#4100)
  .acted.ids      the session called rule_outcome  (new here)
  .checkpoint.ids the rule HELD an act             (#4214)

Every one is an observed tool call. Nothing asks the model what it followed —
milestone 386 ruled that out, because a model asked "did you apply rule 156?"
says yes. Two subtractions: named-minus-opened is the arm talking to nobody,
opened-minus-acted is the milestone's whole subject.

PreCompact stdout is the compaction's custom instructions (#3680), not a
message to the model, so the readout does not say "you slipped" — it says
which ids must be carried through, which is the one thing a summary can do
about an unjudged finding.

SILENT WHEN NOTHING HAPPENED, and the accusations are conditional on having
members. "0 rules unresolved" on every compaction is how a readout teaches
its reader to skip it. Traffic is still reported, because the static
instructions already ask for it in prose; these lines are the measured
version.

scribe_record_outcome.sh is the third ledger's writer, matched on
mcp__.*__rule_outcome and mirroring scribe_record_opened.sh: TMPDIR only,
silent, exit 0 on every path. A PostToolUse hook that spoke would put a line
after every rule_outcome call and give recording an outcome a cost.

Also: check_plugin.py skipped the new hook for want of a smoke event, which
would have left the newest of the three ledgers as the only one the plugin
lane never runs. Added, mirroring its sibling.

tests/test_precompact_hook.py now isolates TMPDIR — the hook reads session
ledgers from there, so without isolation a test would see whatever this real
session had accumulated.

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

plugin/hooks/hooks.json

@@ -62,6 +62,15 @@
             "command": "bash \"${CLAUDE_PLUGIN_ROOT}/hooks/scribe_record_opened.sh\""
           }
         ]
+      },
+      {
+        "matcher": "mcp__.*__rule_outcome",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash \"${CLAUDE_PLUGIN_ROOT}/hooks/scribe_record_outcome.sh\""
+          }
+        ]
       }
     ],
     "PreCompact": [