chore(skills): add feature-planner skill (#5)

Co-authored-by: Ona <no-reply@ona.com>

Author: zacharias-ona

.ona/skills/feature-planner/SKILL.md

@@ -0,0 +1,120 @@
+---
+name: feature-planner
+description: >-
+  Decompose the product vision into a prioritized backlog of GitHub Issues.
+  Reads the product spec, creates issues with acceptance criteria and
+  dependency chains, and sets up labels for the autonomous Feature Builder.
+  Use when starting a new product, adding a new feature area, or
+  re-planning after a scope change.
+  Triggers on "plan features", "create backlog", "decompose spec",
+  "what should we build", "create issues", "plan the product".
+---
+
+# Feature Planner
+
+## When to Use
+
+- Starting a new product from a spec
+- Adding a new feature area to an existing product
+- Re-planning after scope changes or user feedback
+
+## Workflow
+
+### Step 1: Read Context
+
+1. Read `AGENTS.md` for tech stack and conventions.
+2. Read `docs/product-spec.md` for the product vision, scope boundaries, and feature priority.
+3. Read `.agents/architecture.md` for the data model and system design.
+4. List existing GitHub Issues: `gh issue list --state all --json number,title,state,labels`
+5. Identify what's already planned, in progress, or done.
+
+### Step 2: Ensure Labels Exist
+
+Create these labels if they don't exist:
+
+```bash
+gh label create "status:backlog" --color 0E8A16 --force
+gh label create "status:in-progress" --color 1D76DB --force
+gh label create "status:in-review" --color FBCA04 --force
+gh label create "status:done" --color 6F42C1 --force
+gh label create "priority:1" --color B60205 --force
+gh label create "priority:2" --color FF9F1C --force
+gh label create "priority:3" --color 0E8A16 --force
+gh label create "feature" --color A2EEEF --force
+gh label create "enhancement" --color A2EEEF --force
+gh label create "chore" --color FEF2C0 --force
+gh label create "bug" --color D73A4A --force
+gh label create "performance" --color F9D0C4 --force
+```
+
+### Step 3: Decompose into Issues
+
+For each feature, create a GitHub Issue. Each issue must be:
+- **Single-concern**: one independently implementable feature, resulting in one PR
+- **Ordered by dependency**: foundational features first (auth, DB schema, layout)
+- **Sized for one session**: an agent should be able to implement it in a single run
+
+#### Issue Template
+
+```markdown
+## Description
+One paragraph: what this feature does and why a user cares.
+
+## Acceptance Criteria
+- [ ] Criterion 1 (user-visible behavior)
+- [ ] Criterion 2
+- [ ] Criterion 3
+
+## Dependencies
+Depends on #N, #M (or "None")
+
+## Technical Notes
+- Implementation hints, relevant files, patterns to follow
+- Reference .agents/conventions.md for component patterns
+- Reference .agents/architecture.md for data model
+```
+
+#### Labels
+
+Each issue gets exactly 3 labels:
+- **Status**: `status:backlog`
+- **Priority**: `priority:1` (foundation), `priority:2` (core features), `priority:3` (polish/stretch)
+- **Type**: `feature`, `enhancement`, or `chore`
+
+#### Priority Guidelines
+
+| Priority | What belongs here | Examples |
+|---|---|---|
+| `priority:1` | Foundation — nothing else works without this | Auth, workspace CRUD, page CRUD, DB schema, app layout/navigation |
+| `priority:2` | Core features — the product's value | Block editor, slash commands, nested pages, search, realtime |
+| `priority:3` | Polish and stretch goals | Dark mode, responsive design, markdown import/export, member management |
+
+### Step 4: Present the Plan
+
+After creating all issues, present a summary to the user:
+
+```markdown
+## Feature Plan Summary
+
+**Total issues created**: N
+**By priority**: P1: X, P2: Y, P3: Z
+
+### Suggested Implementation Order
+1. #N — Title (P1, no deps)
+2. #M — Title (P1, depends on #N)
+3. ...
+
+### Ambiguities / Questions for Human
+- [Any unclear requirements from the spec]
+- [Any scope decisions that need human input]
+```
+
+Wait for the user to review, reorder, or adjust before the Feature Builder starts picking up issues.
+
+## Anti-patterns
+
+- Do NOT create issues that bundle multiple unrelated changes
+- Do NOT create issues for infrastructure that already exists (check the codebase)
+- Do NOT create overly granular issues (e.g., "add import statement") — each should be a meaningful feature
+- Do NOT create issues without acceptance criteria — the Feature Builder needs them to know when it's done
+- Do NOT assign priority:1 to non-foundational features — P1 means "blocks other work"