docs: add link checks and curation guardrails

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,11 @@
+## Summary
+
+-
+
+## Checklist
+
+- [ ] The tutorial builds a concrete project in C or is clearly useful to C project work.
+- [ ] The entry is in the most specific category and follows the local table format.
+- [ ] The link works, or a working Internet Archive snapshot is used.
+- [ ] Tags are included and match the tag legend in `README.md`.
+- [ ] Multi-part series link directly to a table of contents or list all parts.

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/links.yml

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+name: Links
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+  schedule:
+    - cron: "17 9 * * 1"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  link-check:
+    name: Check Markdown links
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+
+      - name: Check links
+        uses: lycheeverse/lychee-action@v2
+        with:
+          args: >-
+            --root-dir "${{ github.workspace }}"
+            --verbose
+            --no-progress
+            --max-retries 2
+            --retry-wait-time 2
+            --timeout 20
+            --user-agent Mozilla/5.0
+            './**/*.md'
+          fail: true
+          jobSummary: true

.lycheeignore

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+# Browser-facing profiles and tutorial hosts that block automated link checkers.
+^https://github\.com/7etsuo/project-based-tutorials-in-c/actions/workflows/links\.yml/badge\.svg$
+^https://x\.com/tetsuoai$
+^https://medium\.com/from-the-scratch/http-server-what-do-you-need-to-know-to-build-a-simple-http-server-from-scratch-d1ef8945e4fa$
+^https://www\.toptal\.com/game/video-game-physics-part-i-an-introduction-to-rigid-body-dynamics$
+^https://www\.toptal\.com/game/video-game-physics-part-ii-collision-detection-for-solid-objects$
+^https://www\.toptal\.com/game/video-game-physics-part-iii-constrained-rigid-body-simulation$

CONTRIBUTING.md

@@ -4,6 +4,7 @@
     * The use of other programming languages are okay as long as the focus is on C
 * Tutorials should be placed under the correct category (i.e. a game tutorial would go under the Game Development category) and in alphabetical order
 * Links should point to the original tutorial when it works. If the original link is broken or unusable, use a working Internet Archive snapshot.
+* Use tags from the README tag legend where possible, and add focused domain tags for the project area.
 * If submitting a multi-part series that doesn't include a Table of Contents, submit as follows:
     ```
     Title:
@@ -15,3 +16,4 @@
 * If submitting a video series link directly to playlist when possible (i.e. [Learn Video Game Programming in C](https://www.youtube.com/playlist?list=PLT6WFYYZE6uLMcPGS3qfpYm7T_gViYMMt))
 * Mark tutorial(s) with appropriate tags: `book`, `course`, `video`, `in-progress`. (i.e. Handmade Hero `video` `in-progress`)
 * Mark abandoned tutorials with `abandoned` tag (i.e. Handmade Quake `video` `abandoned`)
+* Expect pull requests to run automated link checks. If a live browser link is blocked by automated checkers but still useful, call that out in the PR.