booping transition/vault-commit: plan path and @head resolve against cwd

[A]

Found during an autonomous /develop run (2026-07-09).

Symptoms

1. bin/booping transition <to> plans/<file>.md run from the attached repo root fails with error: plan not found: plans/<file>.md, while the same command with an absolute plan path works. Relative plan paths appear to resolve against cwd instead of the resolved vault.
2. When run from the vault directory instead (workaround attempt), the frontmatter mutations apply but the render-sprints/vault-commit post hooks fail (no project resolved — run from a directory with a .booping marker), leaving a partially-applied transition (status flipped, no sprints refresh, no vault commit).
3. In that same vault-cwd invocation, the frontmatter-update commit=@head hook stamped the vault repo's HEAD sha into commit: instead of the attached repo's HEAD — @head resolves against cwd's git repo.

Expected

• Vault-relative plan paths (plans/<file>.md) resolve against the resolved vault regardless of cwd.
• @head always resolves against the attached repo (the .booping marker's repo), never cwd.
• Post hooks and path resolution should agree on one cwd contract; a transition should either fully apply or fail before mutating.

Workaround: run from the repo root with absolute plan paths.

• case: when plan is relative and /groom run from project repo, it fails to resolve plan from vault and spend time on debugging: