Extend `.gitignore` for dev/gen artifacts

Add ignore rules for commit-msg gen tmp files, nix dev
profiles, vim sessions, macOS metadata, gitea local docs,
and private LLM conversation logs.

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

.gitignore

@@ -102,3 +102,27 @@ venv.bak/
 
 # mypy
 .mypy_cache/
+
+# all files under
+.git/
+
+# any commit-msg gen tmp files
+.claude/*_commit_*.md
+.claude/*_commit*.toml
+
+# nix develop --profile .nixdev
+.nixdev*
+
+# :Obsession .
+Session.vim
+# gitea local `.md`-files
+# TODO? would this be handy to also commit and sync with
+# wtv git hosting service tho?
+gitea/
+
+# ------ macOS ------
+# Finder metadata
+**/.DS_Store
+
+# LLM conversations that should remain private
+docs/conversations/