Stop staging the 9.2 GB ChEMBL DB into every task workdir

GET_FINAL_METABOLITES_STATIC took chembl_db as a `path` input, so Nextflow
copied the ~9.2 GB SQLite DB into each task's work directory. With ~29
concurrent tasks that is hundreds of GB of I/O, against a process that also
declared only 1 GB of memory. Every task failed with exit 1 and retried ten
times, producing 746 errors and an empty 1b_final_metabolites/ output.

Pass the DB as a `val` path instead so tasks read it in place from the
dreamdock-data PVC, and give the process parameterised growing memory.

main.nf

@@ -29,6 +29,14 @@ params.bt_max_retries = 10
 params.bt_fail_action = 'ignore' // 'terminate' or 'ignore'
 params.bt_max_forks = 0             // 0 = unlimited, set to N to limit concurrency
 
+// GET_FINAL_METABOLITES_STATIC — queries the ~9.2 GB ChEMBL SQLite DB on the PVC.
+// The DB is opened read-only/immutable and is NOT staged into the task workdir, so the
+// memory below covers rdkit + the biotransformer CSV, not the database itself.
+params.chembl_initial_memory = 4         // GB - starting memory
+params.chembl_growth_memory  = 4         // GB - additional memory per retry attempt
+params.chembl_max_retries    = 3
+params.chembl_fail_action    = 'ignore'  // 'terminate' or 'ignore' after retries exhausted
+
 //CONPLEX
 params.keep_enst = 'false' //'true' //'false' //to keep individual protein data created by conplex step
 params.conplex_initial_memory = 5   // GB - starting memory for conplex
@@ -121,7 +129,10 @@ workflow {
         default:
             println("Invalid mode specified: ${params.mode}")
     }
-    chembl_ch = Channel.fromPath(params.chembl_db).collect()
+    // Pass the ChEMBL DB as a plain path string rather than a staged file: at ~9.2 GB,
+    // staging it per task copied the DB into every work directory. The process reads it
+    // read-only from the PVC mount instead.
+    chembl_ch = Channel.value(params.chembl_db)
     // GET_FINAL_METABOLITES(HUMAN_TRANSFORMER.out)    // TODO: LOCALIZE
     GET_FINAL_METABOLITES_STATIC(HUMAN_TRANSFORMER.out, chembl_ch)
     //CONPLEX