feat(handoffs): include project identity in all Next Up blocks (#1948) (#2287)

* feat(handoffs): include project identity in all Next Up blocks

Adds project_code and project_title to withProjectRoot() and updates
all 30 Next Up headings across 18 workflow files to include
[PROJECT_CODE] PROJECT_TITLE suffix for multi-project clarity.

Closes #1948

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(review): add withProjectRoot tests and fix placeholder syntax (#1951)

Address code review feedback:
- Add 4 tests for project_code/project_title injection in withProjectRoot()
- Fix inconsistent placeholder syntax in continuation-format.md canonical
  template (bare-brace → shell-dollar to match variant examples)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(phase): preserve zero-padded prefix in renameDecimalPhases

Captures the zero-padded prefix (e.g. "06" from "06.3-slug") with
(0*${baseInt}) so renamed directories keep their original format
(06.2-slug) instead of stripping padding (6.2-slug).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Brandon Higgins <brandonscotthiggins@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

get-shit-done/workflows/execute-phase.md

@@ -1335,7 +1335,7 @@ Items saved to `{phase_num}-HUMAN-UAT.md` — they will appear in `/gsd-progress
 {Gap summaries from VERIFICATION.md}
 
 ---
-## ▶ Next Up
+## ▶ Next Up — [${PROJECT_CODE}] ${PROJECT_TITLE}
 
 `/clear` then: