spec R51: trim default-visible columns to match spec list

R51 lists 11 default-visible columns (clonotype key, dev/integrity
risks, dev score, surfacedMotifCount, exposed/broken cys counts,
PSH/PPC/PNC flags, mode-specific flag). Two columns were visible by
default but not in that list:

- `mode` ("Mode (R7)") flips to optional. The mode prefix is also
  surfaced in the R55 subtitle, so users see it without taking up a
  table column.
- `totalCdrLengthFlag` flips to optional. The raw `totalCdrLength`
  metric is explicitly listed under "Hidden behind show all"; its
  flag follows the same hidden-by-default treatment. Inlined the
  flag column spec (instead of `flagColumnSpec(...)`) since this is
  the only flag with a non-default visibility.

Other 5 deviations flagged during the audit were left alone:
- R25 r12 < 7.5 Å vs ≤ 7.5 Å is measure-zero on continuous distances.
- R39 VHH compactness band edge 1.56 vs 1.57 follows TNP source
  (spec calls it "verbatim"); spec table boundary overlap at 1.57.
- R23 buried-extra-cys "proportionally less via R20 logistic"
  contradicts the R41 hard step (`exposedExtraCysCount × 8.0`); code
  matches the explicit R41 formula.
- R22 cys hit "carries region" not implemented; per-cys PFrame is
  out-of-scope per the refreshed spec ("Out of scope: per-residue
  liability drill-down").

Author: xnacly

workflow/src/specs.lib.tengo

@@ -107,7 +107,7 @@ scoresColumnSpecs := {
 		name: "pl7.app/liabilities/mode",
 		annotations: {
 			"pl7.app/label": "Mode (R7)",
-			"pl7.app/table/visibility": "default",
+			"pl7.app/table/visibility": "optional",
 			"pl7.app/table/orderPriority": "1100"
 		}
 	},
@@ -262,9 +262,21 @@ scoresColumnSpecs := {
 		"pl7.app/liabilities/cdrh3CompactnessLowConfidenceResidueFraction",
 		"CDRH3 compactness low-conf fraction", "740"),
 
-	// R39 three-band threshold flags. Visible by default per R51.
-	totalCdrLengthFlag: flagColumnSpec(
-		"pl7.app/liabilities/totalCdrLengthFlag", "Total CDR length flag", "930"),
+	// R39 three-band threshold flags. Visible by default per R51, except
+	// `totalCdrLengthFlag` which is not in the spec's default-visible list
+	// (totalCdrLength itself is "Hidden behind show all", and its flag
+	// follows the raw metric).
+	totalCdrLengthFlag: {
+		valueType: "String",
+		name: "pl7.app/liabilities/totalCdrLengthFlag",
+		annotations: {
+			"pl7.app/label": "Total CDR length flag",
+			"pl7.app/isScore": "true",
+			"pl7.app/description": _FLAG_DESCRIPTION,
+			"pl7.app/table/visibility": "optional",
+			"pl7.app/table/orderPriority": "930"
+		}
+	},
 	pshFlag: flagColumnSpec(
 		"pl7.app/liabilities/pshFlag", "PSH flag", "970"),
 	ppcFlag: flagColumnSpec(