feat(enhance): LoRA switches per template (#218)

A template can offer optional LoRAs the app turns on or off.

- enhance.toml: [[template.lora]] { id, label, default } per template.
  Each id drives every workflow node titled `imageapi:lora:<id>`, so
  Wan's high- and low-noise pair share one switch.
- POST /enhance takes `loras: {id: bool}`; a missing id uses its default,
  an id the template doesn't offer is a 400. Off sets strength_model
  (and strength_clip when present) to 0, so the graph is never rewired.
- The resolved switches are stored on the job (new enhance_jobs.loras
  JSON column) and returned in the job view, so a retry or adjust can
  repeat them; GET /enhance/templates lists each template's switches.
- A lora-titled node without a declaration keeps its exported strength,
  and a declaration without nodes isn't offered; both are startup
  warnings. A lora-titled node without a numeric strength_model fails
  the template.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/enhance/config.rs

@@ -100,6 +100,30 @@ pub struct TemplateConfig {
     /// Approximate output size, for the client's large-original warning.
     #[serde(default = "default_output_mp")]
     pub output_megapixels: f64,
+    /// Optional LoRAs the app can switch on or off (#218), each matching the
+    /// workflow nodes titled `imageapi:lora:<id>`.
+    #[serde(rename = "lora", default)]
+    pub loras: Vec<LoraConfig>,
+}
+
+/// One LoRA switch (`[[template.lora]]`).
+#[derive(Debug, Clone, PartialEq, Deserialize, serde::Serialize)]
+#[serde(deny_unknown_fields)]
+pub struct LoraConfig {
+    /// Matches the nodes titled `imageapi:lora:<id>` (Wan's high and low
+    /// pair share one id); clients send it in `POST /enhance { loras }`.
+    pub id: String,
+    pub label: String,
+    /// On when the request doesn't say.
+    #[serde(default)]
+    pub default: bool,
+}
+
+/// Template names and LoRA ids: non-empty, letters, digits, `_` and `-`.
+fn valid_id(s: &str) -> bool {
+    !s.is_empty()
+        && s.chars()
+            .all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-')
 }
 
 fn default_join() -> String {
@@ -132,11 +156,7 @@ impl EnhanceConfig {
         }
         let mut seen = std::collections::HashSet::new();
         for t in &self.templates {
-            let ok = !t.name.is_empty()
-                && t.name
-                    .chars()
-                    .all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-');
-            if !ok {
+            if !valid_id(&t.name) {
                 bail!(
                     "template name {:?} must be non-empty and use only letters, digits, '_' and '-'",
                     t.name
@@ -151,6 +171,22 @@ impl EnhanceConfig {
             if t.output_megapixels.is_nan() || t.output_megapixels <= 0.0 {
                 bail!("template {:?}: output_megapixels must be > 0", t.name);
             }
+            let mut ids = std::collections::HashSet::new();
+            for l in &t.loras {
+                if !valid_id(&l.id) {
+                    bail!(
+                        "template {:?}: lora id {:?} must be non-empty and use only letters, digits, '_' and '-'",
+                        t.name,
+                        l.id
+                    );
+                }
+                if !ids.insert(l.id.as_str()) {
+                    bail!("template {:?}: duplicate lora id {:?}", t.name, l.id);
+                }
+                if l.label.trim().is_empty() {
+                    bail!("template {:?}: lora {:?} needs a label", t.name, l.id);
+                }
+            }
         }
         if let Some(d) = &self.default_template
             && !self.templates.iter().any(|t| &t.name == d)
@@ -252,6 +288,31 @@ mod tests {
         assert!(parse("[[path_map]]\nfrom=''\nto='Z:\\\\'").is_err());
     }
 
+    #[test]
+    fn lora_switches_parse_and_validate() {
+        let ok = "[[template]]\nname='a'\nlabel='A'\nfile='a.json'\n\
+                  [[template.lora]]\nid='style'\nlabel='Style'\n\
+                  [[template.lora]]\nid='detail'\nlabel='Detail'\ndefault=true";
+        let cfg = parse(ok).unwrap();
+        let l = &cfg.templates[0].loras;
+        assert_eq!((l[0].id.as_str(), l[0].default), ("style", false));
+        assert_eq!((l[1].id.as_str(), l[1].default), ("detail", true));
+
+        let base = "[[template]]\nname='a'\nlabel='A'\nfile='a.json'\n";
+        let dup = format!(
+            "{base}[[template.lora]]\nid='x'\nlabel='X'\n[[template.lora]]\nid='x'\nlabel='Y'"
+        );
+        assert!(parse(&dup).is_err());
+        assert!(parse(&format!("{base}[[template.lora]]\nid='a b'\nlabel='X'")).is_err());
+        assert!(parse(&format!("{base}[[template.lora]]\nid='x'\nlabel=' '")).is_err());
+        assert!(
+            parse(&format!(
+                "{base}[[template.lora]]\nid='x'\nlabel='X'\nstrength=1"
+            ))
+            .is_err()
+        );
+    }
+
     #[test]
     fn template_defaults() {
         let cfg = parse("[[template]]\nname='a'\nlabel='A'\nfile='a.json'").unwrap();
@@ -259,5 +320,6 @@ mod tests {
         assert_eq!(t.prompt_mode, PromptMode::Append);
         assert_eq!(t.prompt_join, " ");
         assert_eq!(t.output_megapixels, 1.0);
+        assert!(t.loras.is_empty());
     }
 }