Inconsistent Variable Expansion When Using `{{.VAR}}` in `.env` Files with Nested Variables

When using a .env file to define environment variables that rely on other variables using {{.VAR}} template syntax, the variables sometimes expand inconsistently across task runs. The issue becomes more apparent as the variables become more deeply nested.

Steps to Reproduce:

Create a Taskfile.yml:

version: "3"

dotenv: [".env"]

vars:
 BASE_DIR_VAR: "/home/user"
 MID_DIR_VAR: "{{.BASE_DIR_VAR}}/nested"
 FINAL_DIR_VAR: "{{.MID_DIR_VAR}}/deeper"
 FULL_PATH_VAR: "{{.FINAL_DIR_VAR}}/file.txt"

env:
 BASE_DIR_ENV: "/home/user"
 MID_DIR_ENV: "{{.BASE_DIR_ENV}}/nested"
 FINAL_DIR_ENV: "{{.MID_DIR_ENV}}/deeper"
 FULL_PATH_ENV: "{{.FINAL_DIR_ENV}}/file.txt"

tasks:
 show_vars:
   cmds:
     - 'echo "FULL_PATH:     $FULL_PATH"'
     - 'echo "FULL_PATH2:    $FULL_PATH_2"'
     - 'echo "FULL_PATH_VAR: {{.FULL_PATH_VAR}}"'
     - 'echo "FULL_PATH_ENV: {{.FULL_PATH_ENV}}"'
   silent: true

Create a .env File:

BASE_DIR=/home/user
MID_DIR=$BASE_DIR/nested
FINAL_DIR=$MID_DIR/deeper
FULL_PATH=$FINAL_DIR/file.txt
MID_DIR_2={{.BASE_DIR}}/nested
FINAL_DIR_2={{.MID_DIR_2}}/deeper
FULL_PATH_2={{.FINAL_DIR_2}}/file.txt

Run the task multiple times:
```
task show_vars
```

Sample Outputs:

$ task show_vars
FULL_PATH:     /home/user/nested/deeper/file.txt
FULL_PATH2:    /home/user/nested/deeper/file.txt
FULL_PATH_VAR: /home/user/nested/deeper/file.txt
FULL_PATH_ENV: /home/user/nested/deeper/file.txt

$ task show_vars
FULL_PATH:     /home/user/nested/deeper/file.txt
FULL_PATH2:    /nested/deeper/file.txt
FULL_PATH_VAR: /home/user/nested/deeper/file.txt
FULL_PATH_ENV: /home/user/nested/deeper/file.txt

$ task show_vars
FULL_PATH:     /home/user/nested/deeper/file.txt
FULL_PATH2:    /nested/deeper/file.txt
FULL_PATH_VAR: /home/user/nested/deeper/file.txt
FULL_PATH_ENV: /home/user/nested/deeper/file.txt

$ task show_vars
FULL_PATH:     /home/user/nested/deeper/file.txt
FULL_PATH2:    /deeper/file.txt
FULL_PATH_VAR: /home/user/nested/deeper/file.txt
FULL_PATH_ENV: /home/user/nested/deeper/file.txt

Task version:

$ task --version
Task version: 3.39.2 ()

Operating system: macOS 15.1
Experiments enabled: None

go-task / task

Inconsistent Variable Expansion When Using `{{.VAR}}` in `.env` Files with Nested Variables #1847