fix: update /implement and /ship to use alpha as base branch

Author: maxgfr

.claude/skills/implement/SKILL.md

@@ -13,6 +13,15 @@ Implements a GitHub issue end-to-end: understand the issue, code it, validate it
 
 ---
 
+# Step 0 — Detect state
+
+Check if there are already commits on the branch vs `origin/alpha`:
+
+- **No changes on branch** -> Step 1 (start from scratch)
+- **Changes already exist** -> Step 4 (skip to validate)
+
+---
+
 # Step 1 — Understand the issue
 
 Extract `{owner}/{repo}` from `git remote get-url origin` (needed for API calls below).
@@ -31,7 +40,7 @@ Present the task list and confirm with the user before starting.
 
 # Step 2 — Branch
 
-Create `feat/issue-{N}-{slug}` from `origin/master`. If the current branch already tracks this issue, stay on it.
+Create `feat/issue-{N}-{slug}` from `origin/alpha`. If the current branch already tracks this issue, stay on it.
 
 ---
 

.claude/skills/ship/SKILL.md

@@ -22,7 +22,7 @@ Check branch, commits, and existing PR. Route accordingly:
 - **Open PR, nothing unresolved** -> done, report status
 - **No commits on branch** -> nothing to ship, suggest `/implement`
 
-Announce what was detected before proceeding.
+Infer issue number from branch name (`feat/issue-{N}-*`). Announce what was detected before proceeding.
 
 ---
 
@@ -52,7 +52,7 @@ Generated with [Claude Code](https://claude.com/claude-code)
 Group commits by logical concern. Present the plan as a table and ask confirmation. For each group in dependency order:
 
 - Branch naming: `split/{original-branch}/{short-name}`
-- First branch from `origin/master`, each subsequent branch from the previous one
+- First branch from `origin/alpha`, each subsequent branch from the previous one
 - Cherry-pick commits, validate via the validator agent, push, create PR
 
 Cross-link all PRs in their bodies.