docs: fix broken links across documentation guides

[chenopis]

Fix broken GitHub URLs and outdated file paths in documentation:

• fp8-training.md: correct org/repo from NVIDIA/NeMo-Automodel to
  NVIDIA-NeMo/Automodel, fix llama subdirectory (llama → llama3_1)
• finetune.md: update recipe path (finetune.py → train_ft.py),
  fix example script path (examples/llm → examples/llm_finetune)
• gemma3-3n.md: insert missing components/ directory in dataset paths
• pipelining.md: fix all examples/llm/ references to examples/llm_finetune/
• installation.md: fix example script path

Co-authored-by: Cursor cursoragent@cursor.com

What does this PR do ?

Fix 18 broken links across 5 documentation guides. These were identified via a broken link audit of the published docs at docs.nvidia.com/nemo/automodel/. The fixes fall into three categories:

1. Wrong GitHub org/repo (NVIDIA/NeMo-Automodel → NVIDIA-NeMo/Automodel) in fp8-training.md
2. Outdated directory paths after repo restructuring (examples/llm/ → examples/llm_finetune/, nemo_automodel/datasets/ → nemo_automodel/components/datasets/)
3. Renamed files (nemo_automodel/recipes/llm/finetune.py → train_ft.py)

Changelog

• docs/guides/fp8-training.md: Fix GitHub org from NVIDIA/NeMo-Automodel to NVIDIA-NeMo/Automodel in 5 URLs; fix Llama subdirectory from llama/ to llama3_1/
• docs/guides/llm/finetune.md: Update recipe link from finetune.py to train_ft.py; fix example script path from examples/llm/finetune.py to examples/llm_finetune/finetune.py
• docs/guides/omni/gemma3-3n.md: Insert missing components/ directory in 2 dataset URLs (nemo_automodel/datasets/vlm/ → nemo_automodel/components/datasets/vlm/)
• docs/guides/pipelining.md: Fix 7 occurrences of examples/llm/finetune.py → examples/llm_finetune/finetune.py; fix 1 YAML config path (examples/llm/llama_3_2_1b_squad.yaml → examples/llm_finetune/llama3_2/llama3_2_1b_squad.yaml)
• docs/guides/installation.md: Fix example script path from examples/llm/finetune.py to examples/llm_finetune/finetune.py

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[akoumpa]

/ok to test 8b29063