feat: /gsd:ship command for PR creation from verified phase work (#829) (#1123)

* feat: /gsd:ship command for PR creation from verified phase work (#829)

New command that bridges local completion → merged PR, closing the
plan → execute → verify → ship loop.

Workflow (workflows/ship.md):
1. Preflight: verification passed, clean tree, correct branch, gh auth
2. Push branch to remote
3. Auto-generate rich PR body from planning artifacts:
   - Phase goal from ROADMAP.md
   - Changes from SUMMARY.md files
   - Requirements addressed (REQ-IDs)
   - Verification status
   - Key decisions
4. Create PR via gh CLI (supports --draft)
5. Optional code review request
6. Update STATE.md with shipping status

Files:
- commands/gsd/ship.md: New command entry point
- get-shit-done/workflows/ship.md: Full workflow implementation
- get-shit-done/workflows/help.md: Add ship to help output
- docs/COMMANDS.md: Command reference
- docs/FEATURES.md: Feature spec with REQ-SHIP-01 through 05
- docs/USER-GUIDE.md: Add to command table
- CHANGELOG.md: Document new command

Fixes #829

* fix(tests): update expected skill count from 39 to 40 for new ship command

The Copilot install E2E tests hardcode the expected number of skill
directories and manifest entries. Adding commands/gsd/ship.md increased
the count from 39 to 40.

commands/gsd/ship.md

@@ -0,0 +1,23 @@
+---
+name: gsd:ship
+description: Create PR, run review, and prepare for merge after verification passes
+argument-hint: "[phase number or milestone, e.g., '4' or 'v1.0']"
+allowed-tools:
+  - Read
+  - Bash
+  - Grep
+  - Glob
+  - Write
+  - AskUserQuestion
+---
+<objective>
+Bridge local completion → merged PR. After /gsd:verify-work passes, ship the work: push branch, create PR with auto-generated body, optionally trigger review, and track the merge.
+
+Closes the plan → execute → verify → ship loop.
+</objective>
+
+<execution_context>
+@~/.claude/get-shit-done/workflows/ship.md
+</execution_context>
+
+Execute the ship workflow from @~/.claude/get-shit-done/workflows/ship.md end-to-end.