Collapse a pane name's task id in an observation signature

The ledger's first live run showed it: a pane name carries the task id in
lower case, so "phase rotation ...: pane orchestra-<task>-<sha>:1.0 still
holds input" signed differently on every task and could never accumulate
recurrence across them. The id pattern is case-insensitive now.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CVbaKucEYBjMqVeUgJUsc1

internal/domain/observation.go

@@ -90,7 +90,11 @@ func (i ObservationIncident) Key() string {
 }
 
 var (
-	observationID       = regexp.MustCompile(`\b[0-9A-HJKMNP-TV-Z]{26}\b`)
+	// Case-insensitive: a task id appears upper-case in a message and
+	// lower-case inside a pane name, and the live ledger's first run showed
+	// pane names keeping their task, which would give the same failure a
+	// different signature on every task.
+	observationID       = regexp.MustCompile(`(?i)\b[0-9A-HJKMNP-TV-Z]{26}\b`)
 	observationSHA      = regexp.MustCompile(`\b[0-9a-f]{7,64}\b`)
 	observationDuration = regexp.MustCompile(`\b\d+(\.\d+)?(ns|us|µs|ms|s|m|h)(\d+(\.\d+)?(ns|us|µs|ms|s|m|h))*\b`)
 	observationNumber   = regexp.MustCompile(`\b\d+\b`)

internal/operations/observations_test.go

@@ -207,3 +207,14 @@ func TestSignatureCollapsesIdsAndCounts(t *testing.T) {
 		t.Fatal("two different failures collapsed to one signature")
 	}
 }
+
+// The first live run of the ledger caught this: a pane name carries the task
+// id in lower case, so the same failure signed differently on every task and
+// could never accumulate recurrence.
+func TestSignatureCollapsesAPaneName(t *testing.T) {
+	a := domain.ObservationSignature(`phase rotation 06G4XAFH1MBPC35VSJN7V3NS14: pane orchestra-06g4xafh1mbpc35vsjn7v3ns14-be13b045:1.0 still holds input`)
+	b := domain.ObservationSignature(`phase rotation 06G4WW6TND26M16CZA6WE5T458: pane orchestra-06g4ww6tnd26m16cza6we5t458-4d839c05:1.0 still holds input`)
+	if a != b {
+		t.Fatalf("one failure has two signatures:\n%s\n%s", a, b)
+	}
+}