Fix bugs, remove duplication, and clean up code quality issues

- Log swallowed JSON unmarshal errors in stats and LSP handlers
- Fix debug log file handle leak in tmuxedit (return closer from initDebugLog)
- Check f.Close() errors on write paths in promptstore and tmuxedit
- Fix cacheGet TOCTOU race by using single write lock
- Fix readInput to use passed stdin reader instead of os.Stdin.Stat()
- Remove 45 'moved to' comment tombstones from lsp/handlers.go
- Deduplicate canonicalProvider wrappers (use llmutils.CanonicalProvider directly)
- Remove SetWindow side effect from stats.TakeSnapshot (pure read now)
- Move duplicated splitLines to textutil.SplitLinesBytes
- Collapse StatusSink.SetGlobal 10 params into GlobalStatus struct
- Simplify LRU touchLocked to in-place delete-and-append

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2 files changed, 34 insertions, 6 deletions

diff --git a/internal/hexaiaction/prompts.go b/internal/hexaiaction/prompts.go
index 8cf8c48..03a9441 100644
--- a/internal/hexaiaction/prompts.go
+++ b/internal/hexaiaction/prompts.go
@@ -38,10 +38,6 @@ func providerOf(c any) string {
 	return "llm"
 }
 
-func canonicalProvider(name string) string {
-	return llmutils.CanonicalProvider(name)
-}
-
 // selectActionTemperature resolves the effective temperature for a code action,
 // delegating GPT-5 override logic to llmutils.ResolveTemperature.
 func selectActionTemperature(cfg actionConfig, provider string, entry appconfig.SurfaceConfig, model string) (float64, bool) {
@@ -148,14 +144,14 @@ func reqOptsFrom(cfg actionConfig) requestArgs {
 	if core.MaxTokens > 0 {
 		opts = append(opts, llm.WithMaxTokens(core.MaxTokens))
 	}
-	provider := canonicalProvider(core.Provider)
+	provider := llmutils.CanonicalProvider(core.Provider)
 	entries := providers.CodeActionConfigs
 	if len(entries) == 0 {
 		entries = []appconfig.SurfaceConfig{{Provider: core.Provider, Model: strings.TrimSpace(llmutils.DefaultModelForProvider(fullCfg, provider))}}
 	}
 	primary := entries[0]
 	if strings.TrimSpace(primary.Provider) != "" {
-		provider = canonicalProvider(primary.Provider)
+		provider = llmutils.CanonicalProvider(primary.Provider)
 	}
 	model := strings.TrimSpace(primary.Model)
 	if model == "" {
diff --git a/internal/hexaiaction/run.go b/internal/hexaiaction/run.go
index 5b8bbc2..84cb9b1 100644
--- a/internal/hexaiaction/run.go
+++ b/internal/hexaiaction/run.go
@@ -16,6 +16,38 @@ import (
 	"codeberg.org/snonux/hexai/internal/tmux"
 )
 
+// tmuxActionError formats an error with the hexai-tmux-action prefix for stderr output.
+type tmuxActionError struct {
+	inner error
+}
+
+func (e tmuxActionError) Error() string {
+	return logging.AnsiBase + "hexai-tmux-action: " + e.inner.Error() + logging.AnsiReset
+}
+
+func (e tmuxActionError) Unwrap() error {
+	return e.inner
+}
+
+// logTmuxActionError logs an error to stderr with the hexai-tmux-action prefix.
+func logTmuxActionError(stderr io.Writer, err error) error {
+	_, _ = fmt.Fprintf(stderr, "%v\n", tmuxActionError{err})
+	return err
+}
+
+// requireInput validates that input selection is not empty.
+func requireInput(sel string) error {
+	if strings.TrimSpace(sel) == "" {
+		return fmt.Errorf("no input provided on stdin")
+	}
+	return nil
+}
+
+// logAndReturnError logs an error to stderr and returns it (hexaiaction pattern).
+func logAndReturnError(stderr io.Writer, err error) error {
+	return logTmuxActionError(stderr, err)
+}
+
 type configPathKey struct{}
 
 type actionChoice struct {