Added .github

.github/ISSUE_TEMPLATE/bug_report.yml

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+name: Bug report
+description: The kernel doesn't build, doesn't boot, or misbehaves in QEMU
+title: "[Bug]: "
+labels: ["bug"]
+body:
+  - type: textarea
+    id: what
+    attributes:
+      label: What happened?
+      description: What you saw versus what you expected.
+    validations:
+      required: true
+  - type: textarea
+    id: repro
+    attributes:
+      label: Steps to reproduce
+      description: Exact commands, starting from a clean checkout.
+      placeholder: |
+        1. `nasm -f bin boot.asm -o boot.bin`
+        2. `qemu-system-x86_64 -fda boot.bin`
+        3. …
+    validations:
+      required: true
+  - type: textarea
+    id: env
+    attributes:
+      label: Environment
+      description: OS and tool versions.
+      placeholder: |
+        OS: Ubuntu 24.04
+        nasm: 2.16.01 (`nasm -v`)
+        QEMU: 8.2.2 (`qemu-system-x86_64 --version`)
+    validations:
+      required: true
+  - type: textarea
+    id: logs
+    attributes:
+      label: Logs / screenshots
+      description: Paste terminal output or attach a screenshot of the QEMU window.

.github/ISSUE_TEMPLATE/config.yml

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+blank_issues_enabled: true

.github/pull_request_template.md

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+## What does this change do?
+
+<!-- One or two sentences. Link related issues, e.g. "Fixes #123". -->
+
+## Checklist
+
+- [ ] Builds cleanly without error
+- [ ] Boots in QEMU and shows the expected output
+- [ ] No generated artifacts committed (`*.o`, `*.bin`, `*.iso`, `build/` etc)
+- [ ] Documentation updated if behavior changed
+- [ ] AI policy respected: code is human-authored (or fully understood) see [CONTRIBUTING.md](CONTRIBUTING.md)

.github/scripts/check_boot.py

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+"""QEMU boot check for Nadir CI.
+
+Runs the boot sector headless on a pseudo-terminal with the curses display,
+waits for the boot, then asserts the welcome message reached the screen.
+A garbage image (SeaBIOS "No bootable device") fails this check.
+
+Usage: python3 .github/scripts/check_boot.py   (from the repository root)
+Requires: qemu-system-x86_64 on PATH. Stdlib only.
+"""
+
+import fcntl
+import os
+import pty
+import select
+import struct
+import subprocess
+import sys
+import termios
+import time
+
+IMAGE = "boot.bin"
+NEEDLE = b"Nadir"
+BOOT_WAIT_S = 8
+
+
+def main() -> int:
+    master, slave = pty.openpty()
+    fcntl.ioctl(slave, termios.TIOCSWINSZ, struct.pack("HHHH", 24, 80, 0, 0))
+    env = dict(os.environ, TERM="xterm")
+    proc = subprocess.Popen(
+        ["qemu-system-x86_64", "-display", "curses", "-fda", IMAGE],
+        stdin=slave,
+        stdout=slave,
+        stderr=subprocess.DEVNULL,
+        env=env,
+    )
+    os.close(slave)
+    time.sleep(BOOT_WAIT_S)
+    proc.terminate()
+    try:
+        proc.wait(timeout=10)
+    except subprocess.TimeoutExpired:
+        proc.kill()
+        proc.wait()
+    fcntl.fcntl(master, fcntl.F_SETFL, os.O_NONBLOCK)
+    data = b""
+    while True:
+        ready, _, _ = select.select([master], [], [], 1)
+        if not ready:
+            break
+        try:
+            chunk = os.read(master, 65536)
+        except OSError:
+            break
+        if not chunk:
+            break
+        data += chunk
+    os.close(master)
+    if NEEDLE not in data:
+        print(f"FAIL: {NEEDLE!r} not found on the QEMU screen")
+        return 1
+    print("OK: QEMU booted and printed the welcome message")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

.github/workflows/ci.yml

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+# Nadir Kernel CI. Runs on every pull request and every push to main.
+#
+
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  build-and-boot:
+    name: Build and boot in QEMU
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Install toolchain
+        run: sudo apt-get update && sudo apt-get install -y nasm qemu-system-x86
+
+      - name: Build boot sector
+        run: nasm -f bin boot.asm -o boot.bin