Add tmux popup history storage and consolidate state files to XDG_STATE_HOME

- Add StateDir() helper function respecting XDG_STATE_HOME (~/.local/state/hexai/)
- Implement JSONL-based history storage for tmux popup submissions
  - New history.go with AppendHistory() and GetHistory() functions
  - Store timestamp, agent name, cwd, and submitted text
  - Comprehensive unit tests for history functionality
- Integrate history append into tmux edit workflow after successful submission
- Move logs from /tmp/ to persistent state directory:
  - hexai-lsp.log: ~/.local/state/hexai/hexai-lsp.log
  - hexai-tmux-edit.log: ~/.local/state/hexai/hexai-tmux-edit.log
- Update README.md with File Locations section documenting XDG directories
- Fix pre-existing test failures by isolating project config in unit tests
- Panic on state directory creation failure instead of silent fallback

All unit tests pass. Follows XDG Base Directory Specification for proper
state file management with persistence across reboots.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/cmd/hexai-lsp/main.go b/cmd/hexai-lsp/main.go
index 3704cbf..828d0f8 100644
--- a/cmd/hexai-lsp/main.go
+++ b/cmd/hexai-lsp/main.go
@@ -14,7 +14,8 @@ import (
 )
 
 func main() {
-	logPath := flag.String("log", "/tmp/hexai-lsp.log", "path to log file (optional)")
+	defaultLog := defaultLogPath()
+	logPath := flag.String("log", defaultLog, "path to log file (optional)")
 	defaultCfg := defaultConfigPath()
 	configPath := flag.String("config", "", fmt.Sprintf("path to config file (default: %s)", defaultCfg))
 	showVersion := flag.Bool("version", false, "print version and exit")
@@ -37,3 +38,15 @@ func defaultConfigPath() string {
 	}
 	return path
 }
+
+// defaultLogPath returns the default LSP log file path in the state directory.
+// Falls back to /tmp if state directory cannot be determined.
+// defaultLogPath returns the default LSP log file path in the state directory.
+// Panics if state directory cannot be created.
+func defaultLogPath() string {
+	stateDir, err := appconfig.StateDir()
+	if err != nil {
+		panic(fmt.Sprintf("cannot create state directory: %v", err))
+	}
+	return fmt.Sprintf("%s/hexai-lsp.log", stateDir)
+}