perf: add capacity hints to slice allocations

Pre-allocate slices where upper bounds are known: config matches,
migration results, skill search results, search cache, telegram
table extraction, and skill listing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pkg/channels/telegram.go

@@ -833,7 +833,7 @@ func extractInlineCodes(text string) inlineCodeMatch {
 func extractMarkdownTables(text string) tableBlockMatch {
 	lines := strings.Split(text, "\n")
 	out := make([]string, 0, len(lines))
-	tables := make([]string, 0)
+	tables := make([]string, 0, 4)
 	placeholderIdx := 0
 
 	for i := 0; i < len(lines); {
@@ -845,7 +845,7 @@ func extractMarkdownTables(text string) tableBlockMatch {
 			}
 			block := lines[start:i]
 			formatted := formatMarkdownTable(block)
-			placeholder := fmt.Sprintf("\x00TB%d\x00", placeholderIdx)
+			placeholder := "\x00TB" + strconv.Itoa(placeholderIdx) + "\x00"
 			placeholderIdx++
 			tables = append(tables, formatted)
 			out = append(out, placeholder)

pkg/config/config.go

@@ -625,7 +625,7 @@ func (c *Config) GetModelConfig(modelName string) (*ModelConfig, error) {
 
 // findMatches finds all ModelConfig entries with the given model_name.
 func (c *Config) findMatches(modelName string) []ModelConfig {
-	var matches []ModelConfig
+	matches := make([]ModelConfig, 0, 4)
 	for i := range c.ModelList {
 		if c.ModelList[i].ModelName == modelName {
 			matches = append(matches, c.ModelList[i])

pkg/config/migration.go

@@ -45,7 +45,7 @@ func ConvertProvidersToModelList(cfg *Config) []ModelConfig {
 
 	p := cfg.Providers
 
-	var result []ModelConfig
+	result := make([]ModelConfig, 0, 20)
 
 	// Track if we've applied the legacy model name fix (only for first provider)
 	legacyModelNameApplied := false

pkg/skills/loader.go

@@ -70,7 +70,7 @@ func NewSkillsLoader(workspace string, globalSkills string, builtinSkills string
 }
 
 func (sl *SkillsLoader) ListSkills() []SkillInfo {
-	skills := make([]SkillInfo, 0)
+	skills := make([]SkillInfo, 0, 20)
 
 	if sl.workspaceSkills != "" {
 		if dirs, err := os.ReadDir(sl.workspaceSkills); err == nil {

pkg/skills/registry.go

@@ -180,7 +180,7 @@ func (rm *RegistryManager) SearchAll(ctx context.Context, query string, limit in
 		close(resultsCh)
 	}()
 
-	var merged []SearchResult
+	merged := make([]SearchResult, 0, len(regs)*limit)
 	var lastErr error
 
 	var anyRegistrySucceeded bool

pkg/skills/search_cache.go

@@ -39,8 +39,8 @@ func NewSearchCache(maxEntries int, ttl time.Duration) *SearchCache {
 		ttl = 5 * time.Minute
 	}
 	return &SearchCache{
-		entries:    make(map[string]*cacheEntry),
-		order:      make([]string, 0),
+		entries:    make(map[string]*cacheEntry, maxEntries),
+		order:      make([]string, 0, maxEntries),
 		maxEntries: maxEntries,
 		ttl:        ttl,
 	}