Prevent profile file from being overridden by defaults

[endolith]

Describe the changes you have made:

dependent on #1612

1. Update profile.profile_path to the actual path

Previously it was keeping the default:

profile_path: ~/.openinterpreter\default_profile.py

because interpreter.profile_path is not an attribute that would be set
within the profile file, but is a property of that file.

2. Prevent profile from being overridden by defaults

Previously, when loading a custom profile via --profile, its settings
could be overridden by defaults from the initial Profile() instance
because argparse was initialized with those defaults, and
only None-valued arguments would be updated from the custom profile.
This caused issues like custom model settings being reset to the default
claude-3-5-sonnet-20241022.

This change:

• Creates a fresh Profile instance when loading custom profiles
• Tracks which arguments were explicitly provided via CLI
• Updates args from profile unless explicitly set via CLI

This ensures profile settings take precedence over defaults while
still allowing CLI arguments to override profile settings.

Example:
Before: Custom profile with model="gpt-4o-mini" would be overridden
by default model="claude-3-5-sonnet-20241022" unless --model was
explicitly set on command line.

After: Custom profile settings are preserved unless explicitly
overridden by command line arguments.

The provider auto-detection still works as expected:

• If profile sets both model and provider: uses those values
• If profile sets only model: provider=None allows auto-detection

Reference any relevant issues (e.g. "Fixes #000"):

Pre-Submission Checklist (optional but appreciated):

• I have included relevant documentation updates (stored in /docs)
• I have read docs/CONTRIBUTING.md
• I have read docs/ROADMAP.md

OS Tests (optional but appreciated):

• Tested on Windows
• Tested on MacOS
• Tested on Linux