Remove AST-based variable definition resolver and tests

Author: AJenbo

docs/todo/refactor.md

@@ -240,24 +240,6 @@ A minor inefficiency, not a parallel system.
 back to linear scan of `uri_classes_index`. Covers race conditions during initial
 indexing. Legitimate safety net.
 
-### `DIAGNOSTIC_SCOPE` vs `HOVER_SCOPE_CACHE`
-
-Two caches storing the same data type (`ScopeSnapshotMap`) for different consumers.
-`DIAGNOSTIC_SCOPE` is ephemeral/per-pass (build all scopes for the whole file,
-discard on drop). `HOVER_SCOPE_CACHE` is persistent/per-method with content-hash
-invalidation. The split is intentional: diagnostics check every line so they
-build all scopes upfront; hover checks one spot so it lazily caches per-method.
-However, the `is_diagnostic_scope_active()` guard causes ~14 behavioral forks
-in the forward walker, meaning bugs fixed for one consumer may not manifest for
-the other. Unifying them would eliminate the divergent walker behavior.
-
-### Consumer-gated caches
-
-`CALLABLE_TARGET_CACHE`, `PARSE_CACHE`, and `ACTIVE_RESOLVED_CACHE` are activated
-only during diagnostic/analyse passes. Completion and hover re-resolve callable
-targets and re-parse files from scratch. Extending these to all consumers would
-avoid redundant work.
-
 ---
 
 ## Redundant backwards text walkers

src/completion/handler.rs

@@ -400,7 +400,7 @@ impl Backend {
             // ── Variable name completion ────────────────────────────
             // Placed before the interpolation guard so that `"$`
             // and `"{$` both offer variable suggestions.
-            if let Some(response) = Self::try_variable_name_completion(&content, position) {
+            if let Some(response) = self.try_variable_name_completion(&content, position, &uri) {
                 return Ok(Some(response));
             }
 
@@ -1042,12 +1042,16 @@ impl Backend {
     /// Returns `None` when the cursor is not at a variable-name position
     /// or when no variables are found.
     fn try_variable_name_completion(
+        &self,
         content: &str,
         position: Position,
+        uri: &str,
     ) -> Option<CompletionResponse> {
         let partial = Self::extract_partial_variable_name(content, position)?;
+        let symbol_maps = self.symbol_maps.read();
+        let symbol_map = symbol_maps.get(uri).map(|arc| arc.as_ref());
         let (var_items, var_incomplete) =
-            Self::build_variable_completions(content, &partial, position);
+            Self::build_variable_completions(content, &partial, position, symbol_map);
 
         if var_items.is_empty() {
             None