Add GitHub issue pipelines and prompts using gh CLI

gh-issue-impl, gh-issue-research, gh-issue-rewrite, gh-issue-update
pipelines with corresponding prompts for fetch-assess, plan,
implement, and create-pr steps.

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

.wave/prompts/github-issue-impl/create-pr.md

@@ -0,0 +1,76 @@
+You are creating a pull request for the implemented GitHub issue.
+
+Input: {{ input }}
+
+## Working Directory
+
+You are running in an **isolated git worktree** shared with previous pipeline steps.
+Your working directory IS the project root. The feature branch was created by the
+plan step and is already checked out. All git operations here are isolated from
+the main working tree.
+
+Read the issue assessment artifact to find the issue number, repository, branch name, and issue URL.
+
+## SAFETY: Do NOT Modify the Working Tree
+
+This step MUST NOT run `git checkout`, `git stash`, or any command that changes
+the current branch or working tree state. The branch already exists from the
+implement step — just push it and create the PR.
+
+## Instructions
+
+### Step 1: Load Context
+
+From the issue assessment artifact, extract:
+- Issue number and title
+- Repository (`owner/repo`)
+- Branch name
+- Issue URL
+
+### Step 2: Push the Branch
+
+Push the feature branch without checking it out:
+
+```bash
+git push -u origin <BRANCH_NAME>
+```
+
+### Step 3: Create Pull Request
+
+Create the PR using `gh pr create` with `--head` to target the branch. The PR body MUST include `Closes #<NUMBER>` to auto-close the issue on merge.
+
+```bash
+gh pr create --repo <OWNER/REPO> --head <BRANCH_NAME> --title "<concise title>" --body "$(cat <<'EOF'
+## Summary
+<3-5 bullet points describing the changes>
+
+Closes #<ISSUE_NUMBER>
+
+## Changes
+<list of key files changed and why>
+
+## Test Plan
+<how the changes were validated>
+EOF
+)"
+```
+
+### Step 4: Request Copilot Review (Best-Effort)
+
+After the PR is created, attempt to add Copilot as a reviewer:
+```bash
+gh pr edit --add-reviewer "copilot"
+```
+
+This is a best-effort command. If Copilot isn't available in the repository, the command will fail silently and the PR will still be created successfully.
+
+## CONSTRAINTS
+
+- Do NOT spawn Task subagents — work directly in the main context
+- Do NOT run `git checkout`, `git stash`, or any branch-switching commands
+- The PR body MUST contain `Closes #<NUMBER>` to link to the issue
+- Do NOT include Co-Authored-By or AI attribution in commits
+
+## Output
+
+Produce a JSON status report matching the injected output schema.