Add scVelo RNA velocity analysis workflow and IQ-TREE reference documentation

- Introduced a comprehensive RNA velocity analysis pipeline using scVelo, including data loading, preprocessing, velocity estimation, and visualization.
- Added a script for running RNA velocity analysis with customizable parameters and output options.
- Created detailed documentation for IQ-TREE 2 phylogenetic inference, covering command syntax, model selection, bootstrapping methods, and output interpretation.
- Included references for velocity models and their mathematical framework, along with a comparison of different models.
- Enhanced the scVelo skill documentation with installation instructions, use cases, and best practices for RNA velocity analysis.

scientific-skills/gnomad-database/references/graphql_queries.md

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+# gnomAD GraphQL Query Reference
+
+## API Endpoint
+
+```
+POST https://gnomad.broadinstitute.org/api
+Content-Type: application/json
+
+Body: { "query": "<graphql_query>", "variables": { ... } }
+```
+
+## Dataset Identifiers
+
+| ID | Description | Reference Genome |
+|----|-------------|-----------------|
+| `gnomad_r4` | gnomAD v4 exomes (730K individuals) | GRCh38 |
+| `gnomad_r4_genomes` | gnomAD v4 genomes (76K individuals) | GRCh38 |
+| `gnomad_r3` | gnomAD v3 genomes (76K individuals) | GRCh38 |
+| `gnomad_r2_1` | gnomAD v2 exomes (125K individuals) | GRCh37 |
+| `gnomad_r2_1_non_cancer` | v2 non-cancer subset | GRCh37 |
+| `gnomad_cnv_r4` | Copy number variants | GRCh38 |
+
+## Core Query Templates
+
+### 1. Variants in a Gene
+
+```graphql
+query GeneVariants($gene_symbol: String!, $dataset: DatasetId!, $reference_genome: ReferenceGenomeId!) {
+  gene(gene_symbol: $gene_symbol, reference_genome: $reference_genome) {
+    gene_id
+    gene_symbol
+    chrom
+    start
+    stop
+    variants(dataset: $dataset) {
+      variant_id
+      pos
+      ref
+      alt
+      consequence
+      lof
+      lof_flags
+      lof_filter
+      genome {
+        af
+        ac
+        an
+        ac_hom
+        populations { id ac an af ac_hom }
+      }
+      exome {
+        af
+        ac
+        an
+        ac_hom
+        populations { id ac an af ac_hom }
+      }
+      rsids
+      clinvar_variation_id
+      in_silico_predictors { id value flags }
+    }
+  }
+}
+```
+
+### 2. Single Variant Lookup
+
+```graphql
+query VariantDetails($variantId: String!, $dataset: DatasetId!) {
+  variant(variantId: $variantId, dataset: $dataset) {
+    variant_id
+    chrom
+    pos
+    ref
+    alt
+    consequence
+    lof
+    lof_flags
+    rsids
+    genome { af ac an ac_hom populations { id ac an af } }
+    exome { af ac an ac_hom populations { id ac an af } }
+    in_silico_predictors { id value flags }
+    clinvar_variation_id
+  }
+}
+```
+
+**Variant ID format:** `{chrom}-{pos}-{ref}-{alt}` (e.g., `17-43094692-G-A`)
+
+### 3. Gene Constraint
+
+```graphql
+query GeneConstraint($gene_symbol: String!, $reference_genome: ReferenceGenomeId!) {
+  gene(gene_symbol: $gene_symbol, reference_genome: $reference_genome) {
+    gene_id
+    gene_symbol
+    gnomad_constraint {
+      exp_lof exp_mis exp_syn
+      obs_lof obs_mis obs_syn
+      oe_lof oe_mis oe_syn
+      oe_lof_lower oe_lof_upper
+      oe_mis_lower oe_mis_upper
+      lof_z mis_z syn_z
+      pLI
+      flags
+    }
+  }
+}
+```
+
+### 4. Region Query (by genomic position)
+
+```graphql
+query RegionVariants($chrom: String!, $start: Int!, $stop: Int!, $dataset: DatasetId!, $reference_genome: ReferenceGenomeId!) {
+  region(chrom: $chrom, start: $start, stop: $stop, reference_genome: $reference_genome) {
+    variants(dataset: $dataset) {
+      variant_id
+      pos
+      ref
+      alt
+      consequence
+      genome { af ac an }
+      exome { af ac an }
+    }
+  }
+}
+```
+
+### 5. ClinVar Variants in Gene
+
+```graphql
+query ClinVarVariants($gene_symbol: String!, $reference_genome: ReferenceGenomeId!) {
+  gene(gene_symbol: $gene_symbol, reference_genome: $reference_genome) {
+    clinvar_variants {
+      variant_id
+      pos
+      ref
+      alt
+      clinical_significance
+      clinvar_variation_id
+      gold_stars
+      major_consequence
+      in_gnomad
+      gnomad_exomes { ac an af }
+    }
+  }
+}
+```
+
+## Population IDs
+
+| ID | Population |
+|----|-----------|
+| `afr` | African/African American |
+| `ami` | Amish |
+| `amr` | Admixed American |
+| `asj` | Ashkenazi Jewish |
+| `eas` | East Asian |
+| `fin` | Finnish |
+| `mid` | Middle Eastern |
+| `nfe` | Non-Finnish European |
+| `sas` | South Asian |
+| `remaining` | Other/Unassigned |
+| `XX` | Female (appended to above, e.g., `afr_XX`) |
+| `XY` | Male |
+
+## LoF Annotation Fields
+
+| Field | Values | Meaning |
+|-------|--------|---------|
+| `lof` | `HC`, `LC`, `null` | High/low-confidence LoF, or not annotated as LoF |
+| `lof_flags` | comma-separated strings | Quality flags (e.g., `NAGNAG_SITE`, `NON_CANONICAL_SPLICE_SITE`) |
+| `lof_filter` | string or null | Reason for LC classification |
+
+## In Silico Predictor IDs
+
+Common values for `in_silico_predictors[].id`:
+- `cadd` — CADD PHRED score
+- `revel` — REVEL score
+- `spliceai_ds_max` — SpliceAI max delta score
+- `pangolin_largest_ds` — Pangolin splicing score
+- `polyphen` — PolyPhen-2 prediction
+- `sift` — SIFT prediction
+
+## Python Helper
+
+```python
+import requests
+import time
+
+def gnomad_query(query: str, variables: dict, retries: int = 3) -> dict:
+    """Execute a gnomAD GraphQL query with retry logic."""
+    url = "https://gnomad.broadinstitute.org/api"
+    headers = {"Content-Type": "application/json"}
+
+    for attempt in range(retries):
+        try:
+            response = requests.post(
+                url,
+                json={"query": query, "variables": variables},
+                headers=headers,
+                timeout=60
+            )
+            response.raise_for_status()
+            result = response.json()
+
+            if "errors" in result:
+                print(f"GraphQL errors: {result['errors']}")
+                return result
+
+            return result
+        except requests.exceptions.RequestException as e:
+            if attempt < retries - 1:
+                time.sleep(2 ** attempt)  # exponential backoff
+            else:
+                raise
+
+    return {}
+```