Introduce LoraConfig

[lucylq]

Stack from ghstack (oldest at bottom):

• [wip] Support multimethod in export_llama_lib #17231
• [wip] Introduce MultimethodLoraConfig #17230
• -> Introduce LoraConfig #17229
• Support multimethod in runner #17228

Differential Revision: D92304723

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/17229

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❌ 3 New Failures, 2 Unrelated Failures

As of commit 9876e7d with merge base eac0673 ():

NEW FAILURES - The following jobs have failed:

• Lint / lintrunner / linux-job (gh)
• pull / test-lora-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 727d721dd2b3526ef231b52d11550c69c60cca6ddb3ba0e177799b0695a48a9e /exec failed with exit code 1
• pull / unittest-editable / macos / macos-job (gh)
  export/tests/test_target_recipes.py::TestTargetRecipes::test_linear_model

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-samsung-models-linux / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / test-samsung-quantmodels-linux / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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[Copilot]

Pull request overview

This PR introduces a LoraConfig dataclass to encapsulate LoRA (Low-Rank Adaptation) adapter configuration, replacing the previous separate adapter_checkpoint and adapter_config fields in BaseConfig. This refactoring improves code organization and provides a cleaner API for LoRA configuration.

Changes:

• Added LoraConfig dataclass with validation and automatic config parsing from JSON
• Refactored BaseConfig to use LoraConfig instead of separate adapter fields
• Updated from_args method to create LoraConfig instances from CLI arguments
• Simplified adapter loading logic in Llama2Model by using the new LoraConfig object

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
extension/llm/export/config/llm_config.py	Introduces LoraConfig dataclass with validation, updates BaseConfig to use it, and modifies from_args to create LoraConfig from CLI arguments
examples/models/llama/model.py	Refactors adapter loading to use LoraConfig object, simplifying the logic by removing redundant validation and JSON parsing

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[Copilot]

Remove these duplicate imports. The modules json and os are already imported at the top of the file (lines 21-22), so importing them again inside this method is unnecessary.

Suggested change

	import json
	import os

[Copilot]

Import of 'json' is not used.

Suggested change

import json

[Copilot]

Import of 'os' is not used.

Suggested change

import os