Problem: forge tokens were extracted by `parse.body()` which stripped
them from the description, making editing awkward and multi-ref lines
impossible.
Solution: add `find_refs(text)` that scans a string for all forge
tokens by whitespace tokenization, returning byte offsets and parsed
refs without modifying the input. Remove unused `conceal_patterns()`.
Problem: no way to associate tasks with GitHub, GitLab, or Codeberg
issues/PRs, or to track their remote state.
Solution: add `forge.lua` with shorthand (`gh:user/repo#42`) and full
URL parsing, async metadata fetching via `curl`, label formatting,
conceal pattern generation, token resolution, and `refresh()` for
state pull (closed/merged -> done).
