skills: Add /implement and dependencies.

This includes /test-driven-development and /codebase-design

.claude/skills/implement/SKILL.md

@@ -0,0 +1,37 @@
+---
+name: implement
+description: Implement a task file produced by /to-tasks, review it, and close it out.
+disable-model-invocation: true
+---
+
+Implement a task file end-to-end: build it, review it, and close it out.
+
+## Process
+
+### 1. Read the task file and check blockers
+
+The user passes the path to a task file (`.claude/tasks/<NNNN>-slug.md`, as produced by `/to-tasks`) explicitly — don't infer one from context.
+
+If the task's frontmatter has a `blocked-by` field, read each referenced task file and check for any unresolved `- [ ]` acceptance criterion. If any blocker isn't fully resolved, warn the user which one and why, and confirm before proceeding — don't refuse outright.
+
+### 2. Implement
+
+Build the work described in the task's "What to build" section, satisfying its acceptance criteria. Use `/test-driven-development` where possible, at the seams already agreed when the spec or task was written.
+
+Run typechecking regularly, single test files regularly, and the full test suite once at the end.
+
+### 3. Stage the changes
+
+Stage (`git add`) each file you create or modify, specifically — not `git add -A` — so nothing untracked and unrelated gets swept in.
+
+### 4. Review
+
+Run `/review-uncommitted`, passing the task file itself as the spec source — it already links back to its parent spec via its `spec` frontmatter field, if any. Address anything it raises before moving on.
+
+### 5. Close out the task file
+
+Mark every acceptance criterion `[x]` if satisfied or `[-]` if deliberately dropped, so none are left `[ ]`. Append a `## Implementation Notes` section explaining any deviations from the plan — dropped criteria (referencing which, and why), scope changes, decisions made mid-implementation, follow-ups worth flagging. Skip the section only if nothing deviated. Leave the `spec` and `blocked-by` frontmatter fields untouched — they're a permanent record, not a checklist to clear (see `to-tasks`'s `TASK-FORMAT.md`).
+
+Stage the updated task file with the rest.
+
+Do not commit — leave the commit itself for the user to make.