docs: update TODO.md with completed configuration tasks

Mark several completed items in TODO.md:
- Hook system documentation
- Authentication token migration to Doppler
- WSL GPG integration documentation
- mise shell integration
- Windows Terminal settings template
- Global CLAUDE.md addition
- Git configuration expansion (aliases, diff tools, signing)
- GPG configuration setup
- README.md comprehensive refactor
- Deprecated hook migration to TypeScript
- File cleanup/template conversion

Update Git identity configurations:
- Switch Ryan identity to new GPG key (301511AAD64FA365)
- Disable GPG signing for Xevion identity (no key available)
- Add WSL-specific GPG configuration using Windows GPG symlink
- Consolidate Windows/WSL config blocks in dot_gitconfig.tmpl

home/dot_config/git/config-ryan.tmpl

@@ -7,7 +7,7 @@
 [user]
 	name = Ryan Walters
 	email = ryan@walters.to
-	signingkey = 39538EC79ACF2597
+	signingkey = 301511AAD64FA365
 {{ if eq .chezmoi.os "windows" }}
 {{ else }}
 {{ end }}

home/dot_config/git/config-xevion.tmpl

@@ -7,7 +7,7 @@
 [user]
 	name = Xevion
 	email = xevion@xevion.dev
-	signingkey = C217005CF3C00672
+	# No GPG key available for this email - signing disabled
 {{ if eq .chezmoi.os "windows" }}
 {{ else }}
 {{ end }}