feat: implement conditional bond type for mol bond (bd-kzda)

Conditional bonds now work as documented: "B runs only if A fails".

Implementation:
- Add DepConditionalBlocks dependency type to types.go
- Add IsFailureClose() helper to detect failure keywords in close_reason
- Update blocked cache to handle conditional-blocks:
  - B is blocked while A is open
  - B stays blocked if A closes with success
  - B becomes unblocked if A closes with failure

Failure keywords: failed, rejected, wontfix, cancelled, abandoned,
blocked, error, timeout, aborted (case-insensitive)

Updated bondProtoProto, bondProtoMol, bondMolMol to use
DepConditionalBlocks for conditional bond type.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/mol_test.go

@@ -1041,6 +1041,7 @@ func TestSpawnAttachTypes(t *testing.T) {
 	}{
 		{"sequential uses blocks", types.BondTypeSequential, types.DepBlocks},
 		{"parallel uses parent-child", types.BondTypeParallel, types.DepParentChild},
+		{"conditional uses conditional-blocks", types.BondTypeConditional, types.DepConditionalBlocks},
 	}
 
 	for _, tt := range tests {