ci: add LGTM Bot for external contributor merge visibility

.github/LGTM_BOT.md

@@ -0,0 +1,72 @@
+<!--
+SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+# LGTM Bot
+
+Automated merge readiness tracking and AI-powered CI diagnostics.
+
+## What It Does
+
+| Feature | Description |
+|---------|-------------|
+| **`lgtm` label** | Applied when ALL gates pass (CI + approved review + no changes requested). Removed on new pushes. |
+| **Merge Checklist** | Auto-updating PR comment showing CI, review, and merge status at a glance. |
+| **Required Reviewers** | Requests CODEOWNERS team reviews on PR open. Posts a comment for external contributors who cannot see the CODEOWNERS sidebar. |
+| **`/diagnose`** | AI-powered CI failure analysis with root cause and fix suggestions. Groups failures into blocking vs non-blocking. Fetches internal GitLab CI logs for external contributors. |
+
+## Slash Commands
+
+| Command | Access | Description |
+|---------|--------|-------------|
+| `/diagnose` | Any contributor (not first-time) | Analyze CI failures with LLM, grouped by blocking/non-blocking |
+
+## Workflows
+
+| File | Trigger | Purpose |
+|------|---------|---------|
+| `lgtm-bot.yml` | CI completion, reviews, PR sync | Label + checklist + reviewer request |
+| `lgtm-bot-diagnose.yml` | `/diagnose` comment | AI diagnostics (GitHub Actions + GitLab) |
+
+## Secrets
+
+| Secret | Required | Purpose |
+|--------|----------|---------|
+| `GITHUB_TOKEN` | Auto-provided | GitHub API access |
+| `LLM_API_KEY` | Optional | NVIDIA Inference API key for AI analysis |
+| `TOKEN` (GITLAB env) | Optional | GitLab `PRIVATE-TOKEN` for fetching internal CI logs |
+
+## Environment Variables
+
+| Variable | Default | Purpose |
+|----------|---------|---------|
+| `LLM_MODEL` | `nvidia/llama-3.3-70b-instruct` | LLM model name |
+| `LLM_API_BASE_URL` | `https://integrate.api.nvidia.com/v1` | API base URL |
+| `LLM_MAX_RPM` | `10` | Rate limit (requests per minute) |
+
+## Architecture
+
+```
+.github/workflows/lgtm-bot.yml          → label + checklist + CODEOWNERS
+.github/workflows/lgtm-bot-diagnose.yml → /diagnose trigger (env: GITLAB)
+.github/scripts/lgtm_bot_diagnose.py    → consolidated diagnostics entry point
+error_classification/llm_client.py      → LLM API client
+error_classification/config.py          → env config
+```
+
+`lgtm_bot_diagnose.py` handles GitHub Actions checks, GitLab CI log fetching,
+LLM classification, blocking/non-blocking grouping, and comment posting.
+GitHub API via `gh api`; GitLab API via `requests` with `PRIVATE-TOKEN`.

.github/filters.yaml

@@ -58,6 +58,7 @@ ignore:
   - 'container/templates/aws.Dockerfile'
   - 'container/templates/local_dev.Dockerfile'
   - 'container/templates/dev.Dockerfile'
+  - 'error_classification/**'
 
 ci: &ci
   - '.github/workflows/**'