fix(skills): add agent rules for git and db script usage in sprint-start

Spawned agents are told not to run git commands (team lead handles those)
and to call db/connectors scripts with bare commands only — no python3
prefix or command chaining — so they match the permission whitelist.

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

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

@@ -288,6 +288,17 @@ Task(
   prompt: "You are on the {team} team for Sprint {N}.
     Branch: `{team}`
 
+    RULES:
+    - GIT: Do NOT run any git commands (commit, push, pull, merge,
+      checkout, branch, stash, tag, etc.). All git operations are
+      handled by the team lead.
+    - DB SCRIPTS: When calling ticket/sprint/sqlite scripts, use
+      the exact command with no wrappers or chaining. Examples:
+        db/connectors/ticket show 528
+        db/connectors/ticket list --sprint {N}
+      Do NOT prepend python3, do NOT chain with && or ;, do NOT
+      add cleanup commands. Just the bare command.
+
     1. Read the sprint briefing: docs/sprints/sprint-{N}/{team}.md
     2. Read the decision files referenced in the briefing.
     3. Check TaskList for available work.