feat: strengthen git workflow skill guidance

.config/opencode/skills/git-workflow/SKILL.md

@@ -33,9 +33,17 @@ permalink: opencode-config/skills/git-workflow/skill
 ### Creating a worktree for a new feature:
 ```bash
 # From project root
+mkdir -p .worktrees
+git check-ignore -q .worktrees || { printf "Add .worktrees/ to .gitignore before continuing.\n"; exit 1; }
 git worktree add .worktrees/<feature-name> -b <branch-name>
 ```
 
+Before starting feature implementation in the new worktree:
+- Verify `.worktrees/` is the project-local location and ignored by git before creating or reusing worktrees.
+- Run project-declared setup/config scripts if the worktree needs dependencies or generated files.
+- Run a baseline verification (project-declared check/test/lint scripts) to confirm the branch is clean before making changes.
+- If baseline verification fails, stop and diagnose the environment or branch state before coding.
+
 ### Creating multiple worktrees for independent workstreams:
 ```bash
 # From project root — create all worktrees upfront
@@ -48,13 +56,29 @@ git worktree add .worktrees/<workstream-2> -b feat/<workstream-2>
 - Example: `workdir="/path/to/project/.worktrees/my-feature"` for all bash commands.
 - **Each coder invocation must target a specific worktree** — never mix worktrees in one coder dispatch.
 
-### Completing a worktree:
+### After implementation and tests pass: choose one finish path
+
+1. **Merge locally**
+   - Merge `<branch-name>` into your tracked/current base branch, then remove the feature worktree.
+   - If the branch is fully integrated and no longer needed, delete it.
+2. **Push and open PR**
+   - Push `<branch-name>` and create a PR to the base branch using the GitHub PR procedure below.
+   - Keep the worktree until review/merge is complete, then remove the worktree and delete the merged branch.
+3. **Keep branch/worktree for later**
+   - Leave branch and worktree in place when work is paused or awaiting input.
+   - Record the next step and expected resume point so cleanup is not forgotten.
+4. **Discard work (destructive)**
+   - Only for work you explicitly want to throw away.
+   - Require typed confirmation before running destructive commands: `Type exactly: DISCARD <branch-name>`.
+   - After confirmation, remove the worktree and force-delete the unmerged branch with `git branch -D <branch-name>`; this cannot be undone from git alone once commits are unreachable.
+
+### Example local-merge cleanup flow:
 ```bash
-# From main working tree
-git checkout main
+# From the primary working tree
+git checkout <base-branch>
 git merge <branch-name>
 git worktree remove .worktrees/<feature-name>
-git branch -d <branch-name>  # optional cleanup
+git branch -d <branch-name>  # optional cleanup when fully merged
 ```
 
 ### Completing multiple worktrees (independent PRs):