feat(skills): Add plan-awareness to bead workflow skills

- parallel_beads: Filter beads by plan readiness before selection
  - Include beads with plans or type=bug
  - Warn about skipped beads that need plans first
- beads_implement: Check for plan based on bead type
  - Bugs can proceed without plans
  - Features/tasks warn and ask user preference
- beads_workflow: Document design decisions
  - Artifacts vs statuses for phase tracking
  - One bead per feature as default
  - Discovered-work pattern for splitting work

Closes: nixos-configs-45r, nixos-configs-8gr, nixos-configs-oog, nixos-configs-505

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

home/roles/development/skills/beads_workflow.md

@@ -335,3 +335,53 @@ The `shared/` structure still works for non-bead artifacts, but prefer per-bead
 - Keep existing `thoughts/shared/` content
 - New bead-tracked work uses `thoughts/beads-{id}/`
 - Reference old research from bead descriptions when relevant
+
+## Design Decisions
+
+### Phase Tracking: Artifacts vs Statuses
+
+**Current approach**: Skills infer workflow phase from artifact presence:
+- Has `research.md` → research done
+- Has `plan.md` → planning done
+- No artifacts → needs research/planning
+
+**Alternative considered**: Explicit phase statuses (`needs_research`, `needs_plan`, `implementing`, etc.)
+
+**Why artifacts win**:
+1. **Single source of truth** - Status can't drift from reality
+2. **Less state to maintain** - No need to update status when creating artifacts
+3. **Works across repos** - No custom status config needed
+4. **Skills already check artifacts** - Natural fit with existing behavior
+
+**When explicit statuses would help**:
+- Pipeline visualization (e.g., `bd list --status=needs_plan`)
+- Agent self-selection by phase
+- Team coordination dashboards
+
+**Recommendation**: Keep artifact-inference as primary mechanism. If pipeline visibility becomes important, consider adding statuses that skills auto-set when creating artifacts (advisory, not enforced).
+
+### One Bead Per Feature (Default)
+
+**Current approach**: File one bead per logical feature. Skills handle phases internally.
+
+**Alternative considered**: Separate beads for research → planning → implementation, linked by dependencies.
+
+**Why single bead wins for most work**:
+1. **Lower friction** - Quick idea dump without filing 3 tickets
+2. **Simpler tracking** - One status to check
+3. **Natural grouping** - Artifacts stay together in `thoughts/beads-{id}/`
+
+**When to split into multiple beads**:
+- Research reveals the work should be multiple features
+- Different phases need different assignees
+- Explicit dependency tracking matters (e.g., "auth must ship before payments")
+
+**The discovered-work pattern**: Start with one bead. If research reveals split work, file additional beads with dependencies. Skills guide this naturally.
+
+### Plan Requirements by Type
+
+**Bug fixes** (`type=bug`): Can proceed without plans - usually well-scoped from bug report.
+
+**Features/tasks** (`type=feature`, `type=task`): Should have plans - helps ensure design is sound before implementation.
+
+This is advisory, not enforced. Skills warn but allow override for simple changes.