feat(skills): add sprint close + version bump workflow to start-sprint

When invoked on main, /start-sprint now closes the active sprint,
bumps the version to v0.1.N, moves changelog entries under the new
version heading, tags, and pushes. Team branch behavior unchanged.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/start-sprint/SKILL.md

@@ -1,10 +1,12 @@
 ---
 name: start-sprint
 description: >
-  Start sprint work on a team branch. Use when the user says "start sprint",
-  "start working on the server/client/copy", "begin sprint", or invokes
-  /start-sprint. Merges main into the team branch, finds the active sprint,
-  reads the sprint briefing, and presents the work plan with ticket details.
+  Start sprint work on a team branch, or close a sprint from main. Use when
+  the user says "start sprint", "start working on the server/client/copy",
+  "begin sprint", or invokes /start-sprint. On a team branch: merges main,
+  finds the active sprint, reads the briefing, presents the work plan. On
+  main: closes the active sprint, bumps the version (v0.1.N), updates the
+  changelog, tags, and pushes.
 user-invocable: true
 allowed-tools: Bash, Read, Grep, Glob, TeamCreate, Task, TaskCreate, TaskUpdate, TaskList, SendMessage, AskUserQuestion
 ---
@@ -24,7 +26,68 @@ git branch --show-current
 ```
 
 Valid team branches: `server`, `client`, `copy`, `audio`, `visual`, `ci`.
-If on `main`, ask the user which team branch to check out first.
+
+If on `main`, follow the **Main branch workflow** below instead of
+the team branch workflow (steps 2–8).
+
+---
+
+## Main branch workflow (sprint close + version bump)
+
+When `/start-sprint` is run on `main`, it means the user wants to close
+the current sprint, cut a version, and prepare for the next one.
+
+### M1. Close the active sprint
+
+```bash
+db/connectors/sprint stop
+```
+
+This marks the active sprint as completed and lists carry-over candidates.
+Note the sprint number (N) from the output.
+
+### M2. Bump the version
+
+The project version scheme is `v0.1.{sprint_number}`. After closing
+sprint N, the version is `v0.1.N`.
+
+Update `CHANGELOG.md`:
+- Move all entries under `## [Unreleased]` into a new section
+  `## [v0.1.N] — YYYY-MM-DD` (using today's date).
+- Leave `## [Unreleased]` as an empty section above the new version.
+- Keep the existing sub-headings (Added, Fixed, Changed, Removed) —
+  only move entries that have content.
+
+### M3. Commit the release
+
+Stage and commit `CHANGELOG.md`:
+```
+chore(meta): release v0.1.N
+```
+
+### M4. Tag the release
+
+```bash
+git tag v0.1.N
+```
+
+### M5. Push
+
+```bash
+git push && git push --tags
+```
+
+### M6. Report
+
+Output a summary:
+- Sprint closed (name, done/total tickets, carry-over count)
+- Version tagged (`v0.1.N`)
+- Carry-over candidates (if any)
+- Suggest running `/plan-sprint` next to prepare the next sprint
+
+---
+
+## Team branch workflow
 
 ### 2. Sync with main