fix(context): ensure minimum number of search results

Adds MIN_RESULTS constant to guarantee at least 3 results are returned when
searching for related code context, even if they don't meet the similarity
threshold. This improves the quality of contextual responses by preventing
cases where too few results would be returned.

Also adds score normalization for symbol-based search and debug logging for
generated messages.

Author: deathbeam

lua/CopilotChat/client.lua

@@ -427,6 +427,8 @@ function Client:ask(prompt, opts)
     end
   end
 
+  log.debug('Generated messages: ', #generated_messages)
+
   local last_message = nil
   local errored = false
   local finished = false

lua/CopilotChat/context.lua

@@ -69,6 +69,7 @@ local OFF_SIDE_RULE_LANGUAGES = {
 local MIN_SYMBOL_SIMILARITY = 0.3
 local MIN_SEMANTIC_SIMILARITY = 0.4
 local MULTI_FILE_THRESHOLD = 5
+local MIN_RESULTS = 3
 local MAX_FILES = 2500
 
 --- Compute the cosine similarity between two vectors
@@ -103,16 +104,22 @@ local function data_ranked_by_relatedness(query, data, min_similarity)
   local results = {}
   for _, item in ipairs(data) do
     local similarity = spatial_distance_cosine(item.embedding, query.embedding, item.score)
-    if similarity >= min_similarity then
-      table.insert(results, vim.tbl_extend('force', item, { score = similarity }))
-    end
+    table.insert(results, vim.tbl_extend('force', item, { score = similarity }))
   end
 
   table.sort(results, function(a, b)
     return a.score > b.score
   end)
 
-  return results
+  -- Take top MAX_RESULTS items that meet threshold, or at least MIN_RESULTS items
+  local filtered = {}
+  for i, result in ipairs(results) do
+    if (result.score >= min_similarity) or (i <= MIN_RESULTS) then
+      table.insert(filtered, result)
+    end
+  end
+
+  return filtered
 end
 
 -- Create trigrams from text (e.g., "hello" -> {"hel", "ell", "llo"})
@@ -168,7 +175,7 @@ local function data_ranked_by_symbols(query, data, min_similarity)
   local max_score = 0
 
   for _, entry in ipairs(data) do
-    local score = 0
+    local score = entry.score or 0
     local basename = vim.fn.fnamemodify(entry.filename, ':t'):gsub('%..*$', '')
 
     -- Get trigrams for basename and compound version
@@ -201,19 +208,24 @@ local function data_ranked_by_symbols(query, data, min_similarity)
     end
   end
 
-  -- Normalize and filter results
-  local filtered_results = {}
+  -- Normalize scores
   for _, result in ipairs(results) do
     result.score = result.score / max_score
-    if result.score >= min_similarity then
-      table.insert(filtered_results, result)
-    end
   end
 
-  table.sort(filtered_results, function(a, b)
+  -- Sort by score first
+  table.sort(results, function(a, b)
     return a.score > b.score
   end)
 
+  -- Filter results while preserving top scores
+  local filtered_results = {}
+  for i, result in ipairs(results) do
+    if (result.score >= min_similarity) or (i <= MIN_RESULTS) then
+      table.insert(filtered_results, result)
+    end
+  end
+
   return filtered_results
 end