Standardize PR template globally for close-issue command

## Problem Description
The `/close-issue` command is defined as a user-scoped global command (linked to `~/.claude/commands/`), but it assumes each repository has a local `.github/PULL_REQUEST_TEMPLATE.md`. This creates inconsistency and failures when working in repos without PR templates.

## Current State
- Command location: `.claude/command-templates/close-issue.md` → `~/.claude/commands/close-issue.md`
- Command assumes: `.github/PULL_REQUEST_TEMPLATE.md` exists in current repo
- Reality: Many repos don't have PR templates

## Proposed Solution
Following the Snowball Method and dotfiles philosophy:

1. **Create universal PR template**: Store in `~/ppv/pillars/dotfiles/templates/PULL_REQUEST_TEMPLATE.md`
2. **Update close-issue command** to:
- First check for local `.github/PULL_REQUEST_TEMPLATE.md`
- Fall back to dotfiles template if not found
- Use the dotfiles template structure universally
3. **Optional setup.sh enhancement**: Symlink the template to repos during setup

## Benefits
- **Standardization**: Consistent PR format across all projects
- **Provider agnosticism**: Works with GitHub, GitLab, Bitbucket, etc.
- **Reliability**: Global command always has a template to reference
- **Single source of truth**: Update once in dotfiles, applies everywhere

## Implementation Notes
- The PR template should be provider-agnostic (no GitHub-specific fields in required sections)
- The close-issue command should handle both local and global template paths
- Document this pattern as part of the dotfiles standardization approach

## Related Context
This issue was discovered during the post-PR retro for #666, highlighting how systems thinking can reveal improvement opportunities.

Principle: systems-stewardship

Read .claude/command-templates/close-issue.md and inspect the linked ~/.claude/commands/close-issue.md, then review the setup.sh flow and existing templates under pillars/dotfiles/templates/. Confirm how local and global paths are resolved. Done means a provider-agnostic PULL_REQUEST_TEMPLATE.md exists, the command handles both local and fallback templates, and any setup changes are documented.

Written by the indexing model from the issue text.