fix: use absolute paths for gsd-tools.cjs in all install types (#820) (#1062)

Local installs wrote $HOME/.claude/get-shit-done/bin/gsd-tools.cjs into
workflow files, which breaks when GSD is installed outside $HOME (e.g.
external drives, symlinked projects) and when spawned subagents have an
empty $HOME environment variable.

- pathPrefix now always resolves to an absolute path via path.resolve()
- All $HOME/.claude/ replacements use the absolute prefix directly
- Codex installer uses absolute path for get-shit-done prefix
- Removed unused toHomePrefix() function

Tested: 535/535 existing tests pass, verified local install produces
correct absolute paths, verified global install unchanged, verified
empty $HOME scenario resolves correctly.

Closes #820

Made-with: Cursor

Co-authored-by: ralberts3 <ralberts3@gatech.edu>

CHANGELOG.md

@@ -8,6 +8,7 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Fixed
 - OpenCode agent frontmatter conversion — agents now get correct `name:`, `model: inherit`, `mode: subagent` instead of broken command-style conversion that stripped name and kept `color:`/`skills:`/`tools:`
+- Local install: workflow and reference files now get absolute path to `gsd-tools.cjs` instead of `$HOME/.claude/get-shit-done/`, so local installs work when GSD is outside `$HOME` and spawned subagents with empty `$HOME` still resolve the path (#820)
 
 ## [1.23.0] - 2026-03-15