docs: add git howto collection

Two reference files covering:
- git.md — config, daily workflow, diff, log, stash, remotes, tags
- git-branching.md — branches, merge, rebase, cherry-pick, bisect, reflog, reset, revert, worktrees

TODO.md

@@ -2,7 +2,7 @@
 
 ## Topics to Write
 
-- [ ] git — common workflows, rebase, stash, bisect
+- [x] git — config, daily workflow, stash, remotes, branching, rebase, bisect, recovery
 - [x] ansible — playbook patterns, inventory, vault, variables, roles
 - [ ] podman — build, run, compose, volumes
 - [x] jq — filters, select, map, slurp, recipes, @format