ci: set up ai-prompt-auto-commit pre-commit hooks

Adds the pycalendar/ai-prompt-auto-commit hooks so that Claude Code
prompts are automatically appended to commit messages.

- unstage-ai-prompts: keeps .prompts/ out of the index
- append-ai-prompts (prepare-commit-msg): injects prompts into message
- archive-ai-prompts (post-commit): moves .prompts/ to committed/
- prepare-ai-repository (manual): one-time setup already run

Also installs prepare-commit-msg and post-commit git hooks locally.

prompt: ~/.claude/skills/python-project-modernization.md is now updated
  with the https://github.com/pycalendar/ai-prompt-auto-commit tool.
  Please fix set this up for the caldav repo.

AI-generated: This is considered to be CI-infrastructure, one of the
areas identified to be particularly suitable for AI assistance.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: tobixen

.claude/settings.json

@@ -0,0 +1,15 @@
+{
+  "hooks": {
+    "UserPromptSubmit": [
+      {
+        "hooks": [
+          {
+            "id": "ai-prompt-auto-commit",
+            "type": "command",
+            "command": "input=$(cat); ts=$(date +%Y-%m-%dT%H-%M-%S); model=$(printf '%s' \"$input\" | jq -r '.model // \"claude-sonnet-4-6\"'); printf '%s' \"$input\" | jq -r '.prompt' > \".prompts/${ts}_${model}.md\""
+          }
+        ]
+      }
+    ]
+  }
+}

.pre-commit-config.yaml

@@ -14,6 +14,17 @@ repos:
       - id: trailing-whitespace
       - id: end-of-file-fixer
 
+  - repo: https://github.com/pycalendar/ai-prompt-auto-commit
+    rev: v0.0.5
+    hooks:
+      - id: unstage-ai-prompts
+      - id: append-ai-prompts
+        stages: [prepare-commit-msg]
+      - id: archive-ai-prompts
+        stages: [post-commit]
+      - id: prepare-ai-repository
+        stages: [manual]
+
   - repo: https://github.com/compilerla/conventional-pre-commit
     rev: v3.4.0
     hooks: