feat(分支基準): 參考與來源分支一律取遠端 origin，動作前先 fetch

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

skills/implement/SKILL.md

@@ -16,7 +16,7 @@ All wiki reads and writes go through `jsc-gitea:wiki`.
    3. **Never claim a capability tag you have not verified with that script**, and never substitute your own judgement for its verdict. Non-zero exit = blocked: relay the script's message verbatim, stop the skill, do nothing else this turn. Do not run `unlock` to get past the gate; only the user may decide that.
    4. Exit 0 means the stage is locked. From now until the next stage's gate runs, the sdlc-gate hook blocks every prompt whose model stops satisfying the tags.
 2. **Confirm the target branch** — do this **before writing any file**:
-   1. Report the current branch, whether the working tree is clean, and which of `origin/develop` / `origin/master` exist, plus the remote default branch resolved per `references/branch.md`.
+   1. Run `git fetch --prune origin` first — every `origin/...` reference is stale cache without it. Then report the current branch, whether the working tree is clean, which of `origin/develop` / `origin/master` exist, and the remote default branch resolved per `references/branch.md`. **Branches are always the remote ones; local branches are never the basis.**
    2. Ask per `jsc-ask:ask` rules which branch this work merges into; state the impact scope on every option (the answer decides the PR target and, when it collides with the current branch, forces a new working branch).
    3. Uncommitted changes in the working tree → warn first and let the user commit or back them up; never discard them.
    4. Apply `references/branch.md` to the confirmed target: source branch and target branch sharing a name means creating a new working branch instead of committing on the target; report the resulting branch name.
@@ -30,13 +30,13 @@ All wiki reads and writes go through `jsc-gitea:wiki`.
    3. Chose 由使用者輸入 → produce exactly what the user described; do not force the API document layout onto it.
    4. Record the confirmed type in the analysis page's 交付型別 column and save it before starting the todos.
 7. **Create the worktree — before touching any code**. Full rules in `references/branch.md`:
-   1. Read the **source branch** and the repositories involved from the analysis page. Every code change happens inside the worktree; the main working directory's branch and working tree stay untouched.
+   1. Run `git fetch --prune origin`, then read the **source branch** and the repositories involved from the analysis page. The worktree is built from `origin/{來源分支}` — **never from a local branch of the same name**, which may be behind, ahead or diverged. Every code change happens inside the worktree; the main working directory's branch and working tree stay untouched.
    2. Path: `{工作目錄}/.worktree/{分析頁 HASH}/{repo}` — the HASH without the `ANALYZE_` prefix, the repo name without its owner. One worktree per repository, all under the same HASH directory.
-   3. **Ask per `jsc-ask:ask` rules how to handle the branch**, with the two fixed options: create a new working branch off the source branch (`git worktree add -b {工作分支} {路徑} {來源分支}`), or check the source branch out directly (`git worktree add {路徑} {來源分支}`). State the impact scope on each. **Never assume, never skip the question.**
+   3. **Ask per `jsc-ask:ask` rules how to handle the branch**, with the two fixed options: create a new working branch off the remote source branch (`git worktree add -b {工作分支} {路徑} "origin/{來源分支}"`), or check the source branch out with remote tracking (`git worktree add --track -b {來源分支} {路徑} "origin/{來源分支}"`). State the impact scope on each. **Never assume, never skip the question.**
    4. **Quote every branch name and path**: source branches carry Chinese characters, spaces and multiple slashes (for example `feat/一址通/查地址/完整版/P2`), and an unquoted argument gets split.
    5. No local clone of that repository → stop and ask the user for its path; never clone on your own initiative and never guess the location.
    6. Add `.worktree/` to that repository's `.git/info/exclude` — never edit the user's shared `.gitignore`.
-   7. Report the worktree path, the checked-out branch and the source branch. Completion condition: every involved repository has a worktree and you have reported all of them.
+   7. Report the worktree path, the checked-out branch, the source branch and the commit sha `origin/{來源分支}` pointed at — that sha is this implementation's starting point and must stay traceable. Completion condition: every involved repository has a worktree and you have reported all of them.
 8. List every open item of the work package and implement them **one at a time**, **inside the worktree**:
    - Follow the TDD loop: red before green, one slice at a time; rules and anti-patterns in `references/tdd.md` (refactoring belongs to the review stage).
    - After each item, flip its `[ ]` to `[x]` on the analysis page and save to the wiki before starting the next item.