fix(lsp): context-aware completions now use correct token variants

The Logos lexer produces dedicated token variants for all keywords
(Token::Behavior, Token::LifeArc, etc.) — Token::Ident is only for
user-defined identifiers. determine_context() was matching against
Token::Ident(keyword), so last_keyword was always None and every
nested block returned CompletionContext::Unknown, causing
all_keyword_completions() to dump top-level declaration keywords
everywhere.

Changes:
- determine_context(): match actual token variants (Token::Behavior,
  Token::LifeArc, Token::Relationship, Token::Character, etc.) and
  track last_context directly instead of a String keyword
- behavior_keyword_completions(): add all word-based BT keywords
  (choose, then, repeat, if, when, invert, retry, timeout, cooldown,
  succeed_always, fail_always)
- InFieldBlock arm: always include field_keyword_completions() so
  generic fields (age, bond, etc.) appear even without a species
- Tests: add negative assertions confirming top-level keywords are
  absent inside behavior/life_arc blocks; add new test
  test_behavior_no_toplevel_keywords for nested block isolation

src/lsp/completion_tests.rs

@@ -110,10 +110,33 @@ mod tests {
         if let Some(response) = result {
             match response {
                 | tower_lsp::lsp_types::CompletionResponse::Array(items) => {
-                    // Should have behavior tree keywords
+                    // Should have symbolic behavior tree keywords
                     assert!(items.iter().any(|item| item.label == "?"));
                     assert!(items.iter().any(|item| item.label == ">"));
                     assert!(items.iter().any(|item| item.label == "*"));
+                    // Should have word-based behavior tree keywords
+                    assert!(items.iter().any(|item| item.label == "choose"));
+                    assert!(items.iter().any(|item| item.label == "then"));
+                    assert!(items.iter().any(|item| item.label == "repeat"));
+                    assert!(items.iter().any(|item| item.label == "if"));
+                    assert!(items.iter().any(|item| item.label == "when"));
+                    // Should NOT have top-level declaration keywords
+                    assert!(
+                        !items.iter().any(|item| item.label == "institution"),
+                        "institution should not appear inside behavior block"
+                    );
+                    assert!(
+                        !items.iter().any(|item| item.label == "species"),
+                        "species should not appear inside behavior block"
+                    );
+                    assert!(
+                        !items.iter().any(|item| item.label == "character"),
+                        "character should not appear inside behavior block"
+                    );
+                    assert!(
+                        !items.iter().any(|item| item.label == "location"),
+                        "location should not appear inside behavior block"
+                    );
                 },
                 | _ => panic!("Expected array response"),
             }
@@ -136,6 +159,61 @@ mod tests {
                     // Should have life arc keywords
                     assert!(items.iter().any(|item| item.label == "state"));
                     assert!(items.iter().any(|item| item.label == "on"));
+                    // Should NOT have top-level declaration keywords
+                    assert!(
+                        !items.iter().any(|item| item.label == "institution"),
+                        "institution should not appear inside life_arc block"
+                    );
+                    assert!(
+                        !items.iter().any(|item| item.label == "behavior"),
+                        "behavior should not appear inside life_arc block"
+                    );
+                    assert!(
+                        !items.iter().any(|item| item.label == "character"),
+                        "character should not appear inside life_arc block"
+                    );
+                },
+                | _ => panic!("Expected array response"),
+            }
+        }
+    }
+
+    #[test]
+    fn test_behavior_no_toplevel_keywords() {
+        // Cursor inside nested `then` block — context should remain InBehavior
+        let source = "behavior Test {\n    then {\n        \n    }\n}";
+        let doc = Document::new(source.to_string());
+        // Position inside nested then block (line 2, after spaces)
+        let params = make_params(2, 8);
+
+        let result = completion::get_completions(&doc, &params);
+        assert!(result.is_some());
+
+        if let Some(response) = result {
+            match response {
+                | tower_lsp::lsp_types::CompletionResponse::Array(items) => {
+                    // Behavior keywords should still be present at any nesting depth
+                    assert!(
+                        items.iter().any(|item| item.label == "?"),
+                        "? should appear in nested behavior block"
+                    );
+                    assert!(
+                        items.iter().any(|item| item.label == "choose"),
+                        "choose should appear in nested behavior block"
+                    );
+                    // Top-level keywords must not appear
+                    assert!(
+                        !items.iter().any(|item| item.label == "institution"),
+                        "institution must not appear in nested behavior block"
+                    );
+                    assert!(
+                        !items.iter().any(|item| item.label == "species"),
+                        "species must not appear in nested behavior block"
+                    );
+                    assert!(
+                        !items.iter().any(|item| item.label == "character"),
+                        "character must not appear in nested behavior block"
+                    );
                 },
                 | _ => panic!("Expected array response"),
             }