sdd-workspace slugged workspaces by basename alone, so docs/alpha/plan.md
and docs/beta/plan.md resolved to one directory and task-brief silently
overwrote the other plan's brief — the single gitignored source of task
requirements, unrecoverable once clobbered.
Each workspace now records its owning plan in a plan-path marker
(repo-relative in-repo, absolute outside). Lookup keeps basename slugs
and existing behavior for the common case: a markerless workspace is
adopted in place (no migration break for in-flight plans), a marker
naming this plan is a match, and a marker naming a different plan
disambiguates with the plan's parent-directory name, then a counter.
Plan paths are normalized (CDPATH-guarded physical cd) so relative,
absolute, and ../ spellings of one plan share one workspace.
task-brief and review-package delegate to sdd-workspace and need no
changes. SKILL.md's workspace bullet no longer promises the exact
<plan-basename> path, since disambiguated workspaces differ.
Reported by @CRGDan; reproduction and test groundwork by @crisnahine
in PR #2120.
Fixes#2045
sdd-workspace now requires the plan file and resolves
.superpowers/sdd/<plan-basename>/; task-brief and review-package write
into their plan's directory (review-package gains PLAN_FILE as its first
argument). Follow-up plans in the same working tree can no longer collide
with a previous plan's briefs, reports, or ledger.
Jesse Vincent