feat(tools): add exec tool enhancement with background execution and PTY support (#1752)

- Unified exec tool with actions: run/list/poll/read/write/send-keys/kill
- PTY support using creack/pty library
- Process session management with background execution
- Process group kill for cleaning up child processes
- Session cleanup: 30-minute TTL for old sessions
- Output buffer: 100MB limit with truncation

Actions:
- run: execute command (sync or background)
- list: list all sessions
- poll: check session status
- read: read session output
- write: send input to session stdin
- send-keys: send special keys (up, down, ctrl-c, enter, etc.)
- kill: terminate session

Tests:
- PTY: allowed commands, write/read, poll, kill, process group kill
- Non-PTY: background execution, list, read, write, poll, kill, process group kill
- Session management: add/get/remove/list/cleanup

pkg/tools/types.go

@@ -56,3 +56,24 @@ type ToolFunctionDefinition struct {
 	Description string         `json:"description"`
 	Parameters  map[string]any `json:"parameters"`
 }
+
+type ExecRequest struct {
+	Action     string            `json:"action"`
+	Command    string            `json:"command,omitempty"`
+	PTY        bool              `json:"pty,omitempty"`
+	Background bool              `json:"background,omitempty"`
+	Timeout    int               `json:"timeout,omitempty"`
+	Env        map[string]string `json:"env,omitempty"`
+	Cwd        string            `json:"cwd,omitempty"`
+	SessionID  string            `json:"sessionId,omitempty"`
+	Data       string            `json:"data,omitempty"`
+}
+
+type ExecResponse struct {
+	SessionID string        `json:"sessionId,omitempty"`
+	Status    string        `json:"status,omitempty"`
+	ExitCode  int           `json:"exitCode,omitempty"`
+	Output    string        `json:"output,omitempty"`
+	Error     string        `json:"error,omitempty"`
+	Sessions  []SessionInfo `json:"sessions,omitempty"`
+}