SAM Python Debugger fails to respect breakpoints in VSC when DockerContext is modified to ./

## Problem
SAM Python Debugger fails to respect breakpoints in VSC when `DockerContext` is modified to `./`

## Steps to reproduce the issue

1. Create new SAM application using the VSCode toolkit
2. Modify `template.yaml` from:
```
Metadata:
Dockerfile: Dockerfile
DockerContext: ./hello_world
DockerTag: python3.12-v1
```
to
```
Metadata:
Dockerfile: hello_world/Dockerfile
DockerContext: ./
DockerTag: python3.12-v1
```
4. Modify `Dockerfile` (`COPY ./hello_world/app.py requirements.txt ./`) to use the correct path.
5. Set breakpoint in app.py
6. Debug function (using either of the default debug configurations).
7. Function launches, debugger attaches, but breakpoints are not respected

## Expected behaviour

Function launches, debugger attaches, and breakpoints are respected

## System details (run `AWS: About` and/or `Amazon Q: About`)
```
OS: Darwin arm64 23.5.0
Visual Studio Code extension host: 1.91.1
AWS Toolkit: 3.15.0
node: 20.9.0
electron: 29.4.0
```
Should it make a difference, I am using Colima instead of Docker.
```
colima version 0.6.9
```

Reproduce the issue using template.yaml, hello_world/Dockerfile, and app.py with DockerContext set to ./; start with the default VS Code debug configurations. Trace how the debugger maps the container and workspace paths, then verify that breakpoints in app.py are respected when the function launches through Colima or Docker.

Written by the indexing model from the issue text.