feat(memo): replace custom omemo with mattn/memo template

[edge2992]

Summary

• Delete dot_local/bin/omemo (custom shell script that duplicated mattn/memo's functionality).
• Wire up mattn/memo's built-in template feature instead, by bringing ~/.config/memo/ under chezmoi management.
• Parameterize the memo vault path via a new chezmoi template variable memo_dir so the public repo no longer hardcodes a personal vault name.

Changes

File	Change	Purpose
dot_local/bin/omemo	deleted	Functionality moved to memo template
private_dot_config/memo/template.md	added	mattn/memo template ({{.Title}}, {{.Date}}) producing the same YAML frontmatter omemo did
private_dot_config/memo/config.toml.tmpl	added	chezmoi-managed memo config; memodir and memotemplate use ${HOME} and {{ .memo_dir }}
.chezmoi.yaml.tmpl	+1 prompt	New memo_dir data var (default Documents/memo/_posts)
.pre-commit-config.yaml	exclude .chezmoi.yaml.tmpl	The hook calls chezmoi execute-template which doesn't know promptStringOnce

Why this approach

1. mattn/memo is already installed via run_once_install-linux-packages.sh.tmpl:59. Its memotemplate config supports the exact use case the omemo script was solving.
2. Per mattn/memo README, memodir/memotemplate accept ${HOME} and ~/ — using ${HOME} makes the path portable across machines without hardcoding /home/<user> or /Users/<user>.
3. The vault name ob_edgissa is personal; moving it to a chezmoi prompt keeps it out of git while letting first-time chezmoi init set it up.

Post-merge steps (for me)

After merging:

# Add memo_dir to personal chezmoi config
$EDITOR ~/.config/chezmoi/chezmoi.yaml
#   data:
#     memo_dir: "Documents/ob_edgissa/memo/_posts"

chezmoi diff   # confirms config.toml + template.md additions
chezmoi apply
memo new "test"   # smoke test — should open nvim with frontmatter

A separate cleanup is needed: branch fix/omemo-executable-prefix was an earlier (now superseded) attempt to keep the script. It should be deleted with git push origin --delete fix/omemo-executable-prefix after this PR is merged.

Test plan

• make lint passes
• pre-commit run --all-files passes for changed files
• chezmoi execute-template < private_dot_config/memo/config.toml.tmpl renders cleanly with default and after memo_dir is set
• After merge: memo new "test" produces a markdown file with the expected frontmatter at \$memo_dir