feat: named template bookmarks in user config

[raiderrobert]

Problem

Power users frequently install the same handful of templates and don't want to retype shortcodes/URLs. Shell aliases don't cross machines, and the existing [abbreviations] table is a prefix URL-rewriter — not a name-to-URL bookmark.

Proposed feature

A new [templates] section in ~/.config/diecut/config.toml:

[templates]
rust-cli = "gh:raiderrobert/templates/rust-cli"
py-pkg   = "https://github.com/raiderrobert/python-package-template"
work     = "https://git.company.com/platform/scaffold.git"

Resolution: diecut new rust-cli → looks up rust-cli in [templates] → value is resolved via the normal pipeline (shortcode, URL, or local path) → clone.

CLI helpers:

diecut alias add rust-cli gh:user/templates/rust-cli
diecut alias remove rust-cli
diecut alias list

Design notes

• [templates] is distinct from [abbreviations] — one is exact-name lookup, the other is prefix rewriting. Both coexist.
• Recursive resolution of a bookmark value is restricted to one level (a bookmark can't point at another bookmark) to prevent cycles.

Open questions

• Precedence vs. shortcodes: if a bookmark is named gh, does it shadow the gh: prefix? Lean: reserve names matching known prefixes, reject at alias add time.
• alias add without a name → auto-derive from last path segment of URL?

Acceptance criteria

• [templates] config section parsed
• Name-based lookup in diecut new pipeline
• diecut alias {add, remove, list} subcommands
• Cycle / shadow-name guards
• Tests
• Docs