chore: import upstream snapshot with attribution

.github/FUNDING.yml

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+github: [rohitg00]
+custom: ["https://github.com/rohitg00/ai-engineering-from-scratch/blob/main/SPONSORS.md"]

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Something in a lesson or on the site is wrong
+title: "[bug] "
+labels: bug
+---
+
+## Where
+
+- Phase / lesson: <!-- e.g. Phase 4 · 06-object-detection-yolo -->
+- File / URL: <!-- e.g. phases/04-computer-vision/06-object-detection-yolo/code/main.py or aiengineeringfromscratch.com/lesson.html?path=... -->
+
+## What's wrong
+
+<!-- One-paragraph description. What did you expect vs. what you saw. -->
+
+## Reproduce
+
+1.
+2.
+3.
+
+## Environment
+
+- OS:
+- Python / Node / other runtime version:
+- How you ran it (local, Colab, Docker, etc.):
+
+## Screenshot or logs
+
+<!-- Drop a screenshot or paste the traceback if you have one. -->

.github/ISSUE_TEMPLATE/new_lesson_proposal.md

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+---
+name: New lesson proposal
+about: Pitch a lesson before writing it
+title: "[lesson] Phase NN · "
+labels: new-lesson
+---
+
+## Lesson
+
+- Phase: <!-- e.g. Phase 5 (NLP) -->
+- Proposed number: <!-- e.g. 03 (lessons are numbered within a phase) -->
+- Working title:
+- Type: Build | Learn
+- Languages: <!-- Python, TypeScript, Rust, Julia -->
+- Estimated time: <!-- e.g. ~75 min -->
+
+## Why it belongs
+
+<!-- Two or three sentences. What can't a learner do without this lesson? Why here in the sequence? -->
+
+## Prerequisites
+
+<!-- Which prior lessons does this depend on? -->
+
+## What the learner ships
+
+<!-- Every lesson produces a reusable artifact. Which one? -->
+
+- [ ] Prompt
+- [ ] Skill
+- [ ] Agent
+- [ ] MCP server
+- [ ] Tool / script
+
+## Outline
+
+1. **The Problem** — what pain does this solve?
+2. **The Concept** — core mental model, no code yet
+3. **Build It** — from-scratch implementation plan
+4. **Use It** — which framework / library to show after
+5. **Ship It** — the artifact to produce
+6. **Exercises** — 3 proposed
+
+## Open questions
+
+<!-- Anything you want input on before starting. -->

.github/PULL_REQUEST_TEMPLATE.md

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+<!-- Thanks for contributing. Fill out what applies. Delete sections that don't. -->
+
+## What this PR does
+
+<!-- One-sentence summary. -->
+
+## Kind of change
+
+- [ ] New lesson
+- [ ] Fix to an existing lesson
+- [ ] Translation
+- [ ] New output (prompt, skill, agent, MCP server)
+- [ ] Docs / website / tooling
+
+## Checklist
+
+- [ ] Code runs without errors with the listed dependencies
+- [ ] No comments in code files (docs explain, code is self-explanatory)
+- [ ] Built from scratch first, then shown with a framework (for new lessons)
+- [ ] Lesson folder matches `LESSON_TEMPLATE.md` structure
+- [ ] ROADMAP.md row for the lesson is a markdown link (`[Name](phases/...)`), not bare text
+- [ ] One lesson per commit (atomic per-lesson rule)
+- [ ] Tested locally / code output matches what `docs/en.md` claims
+
+## Phase / lesson
+
+<!-- e.g. Phase 5 · 03-tokenizers -->
+
+## Notes for reviewer
+
+<!-- Anything surprising, any deviations from the template, open questions. -->

.github/workflows/curriculum.yml

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+name: curriculum
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "phases/**"
+      - "scripts/audit_lessons.py"
+      - "scripts/build_catalog.py"
+      - "scripts/check_readme_counts.py"
+      - "README.md"
+      - "ROADMAP.md"
+      - "glossary/**"
+      - "site/build.js"
+      - ".github/workflows/curriculum.yml"
+  pull_request:
+    branches: [main]
+    paths:
+      - "phases/**"
+      - "scripts/audit_lessons.py"
+      - "scripts/build_catalog.py"
+      - "scripts/check_readme_counts.py"
+      - "README.md"
+      - "ROADMAP.md"
+      - "glossary/**"
+      - "site/build.js"
+      - ".github/workflows/curriculum.yml"
+
+permissions:
+  contents: read
+
+jobs:
+  audit:
+    name: invariant checks
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+        with:
+          persist-credentials: false
+      - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065  # v5
+        with:
+          python-version: "3.12"
+      - name: run scripts/audit_lessons.py
+        run: python3 scripts/audit_lessons.py
+
+  readme-counts-sync:
+    name: README counts auto-fix (main only)
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    if: github.event_name == 'push'
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+        with:
+          ref: ${{ github.ref }}
+          token: ${{ secrets.GITHUB_TOKEN }}
+      - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065  # v5
+        with:
+          python-version: "3.12"
+      - name: build ephemeral catalog
+        run: python3 scripts/build_catalog.py
+      - name: sync README counts
+        run: python3 scripts/check_readme_counts.py --fix
+      - name: commit + push if README changed
+        env:
+          BOT_COMMIT_PREFIX: "chore(readme): sync counts"
+        run: |
+          if git diff --quiet README.md; then
+            echo "README.md already in sync"
+            exit 0
+          fi
+          last_msg=$(git log -1 --pretty=%s)
+          if [[ "$last_msg" == "$BOT_COMMIT_PREFIX"* ]]; then
+            echo "last commit was already a bot regen; not pushing to avoid loop"
+            exit 0
+          fi
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add README.md
+          git commit -m "$BOT_COMMIT_PREFIX"
+          # Retry on non-fast-forward when another merge to main races us
+          branch="${GITHUB_REF#refs/heads/}"
+          for attempt in 1 2 3 4 5; do
+            if git push origin "HEAD:${branch}"; then
+              echo "push succeeded on attempt $attempt"
+              exit 0
+            fi
+            echo "push attempt $attempt rejected; rebasing onto origin/${branch}"
+            git fetch origin "${branch}"
+            if ! git rebase "origin/${branch}"; then
+              echo "rebase produced a conflict; aborting and giving up cleanly"
+              git rebase --abort || true
+              exit 0
+            fi
+            sleep "$((attempt * 2))"
+          done
+          echo "push failed after 5 attempts; main will self-heal on next push"
+          exit 0
+
+  site-rebuild:
+    name: site/data.js auto-rebuild (main only)
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    needs: readme-counts-sync
+    if: github.event_name == 'push'
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+        with:
+          ref: ${{ github.ref }}
+          token: ${{ secrets.GITHUB_TOKEN }}
+      - name: rebuild site/data.js
+        run: node site/build.js
+      - name: commit + push if site/data.js changed
+        env:
+          BOT_COMMIT_PREFIX: "chore(site): rebuild data.js"
+        run: |
+          if git diff --quiet site/data.js; then
+            echo "site/data.js already in sync"
+            exit 0
+          fi
+          last_msg=$(git log -1 --pretty=%s)
+          if [[ "$last_msg" == "$BOT_COMMIT_PREFIX"* ]]; then
+            echo "last commit was already a bot regen; not pushing to avoid loop"
+            exit 0
+          fi
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add site/data.js
+          git commit -m "$BOT_COMMIT_PREFIX"
+          branch="${GITHUB_REF#refs/heads/}"
+          for attempt in 1 2 3 4 5; do
+            if git push origin "HEAD:${branch}"; then
+              echo "push succeeded on attempt $attempt"
+              exit 0
+            fi
+            echo "push attempt $attempt rejected; rebasing onto origin/${branch}"
+            git fetch origin "${branch}"
+            if ! git rebase "origin/${branch}"; then
+              echo "rebase produced a conflict; aborting and giving up cleanly"
+              git rebase --abort || true
+              exit 0
+            fi
+            sleep "$((attempt * 2))"
+          done
+          echo "push failed after 5 attempts; main will self-heal on next push"
+          exit 0
+
+  readme-counts-drift:
+    name: README.md counts drift advisory
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+        with:
+          persist-credentials: false
+      - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065  # v5
+        with:
+          python-version: "3.12"
+      - name: build ephemeral catalog
+        run: python3 scripts/build_catalog.py
+      - name: check README counts
+        run: |
+          if ! python3 scripts/check_readme_counts.py; then
+            echo "::warning::README.md counts drift detected. Main will self-heal on merge."
+          fi