docs: add squash commit guidance to PR template

[JSRRosenbaum]

Description

Adds a real PR template at .github/pull_request_template.md and includes a suggested squash-commit section so reviewers have the merge commit message in the PR body before approval.

Why this exists:

• PR fix: stabilize CLI setup developer experience #8 needed a squash commit message after the fact.
• The existing template was under .github/workflows/, where GitHub does not use it as the repository PR template.
• This keeps the expectation shifted left: every future PR should state scope, verification, follow-up/out-of-scope items, and the proposed squash message up front.

Suggested squash commit

docs: add squash commit guidance to PR template

Move the pull request template to GitHub's recognized location and require a suggested squash commit block so PR authors provide merge-message intent during review instead of after approval.

- move PR template from .github/workflows to .github/pull_request_template.md
- add Suggested squash commit section with subject/body/bullets/verification shape
- add explicit manual verification, quality gates, and out-of-scope follow-up prompts

Verified with template path assertions, markdown whitespace checks, and shell syntax checks.

Type of Change

• 🐛 Bug Fix
• 🚀 New Feature
• 🧹 Refactor
• 📝 Documentation

Testing & Verification

• Automated test suites pass locally.
• Changes verified manually in a local environment.

Manual verification run:

• test -f .github/pull_request_template.md
• test ! -f .github/workflows/pull_request_template.md
• grep -q "Suggested squash commit" .github/pull_request_template.md
• grep -q "Known Follow-up / Out of Scope" .github/pull_request_template.md

Quality gates run:

• Markdown final-newline/trailing-whitespace assertion
• bash -n setup.sh ctx

Checklist

• My code adheres to the style guidelines of this repository.
• I have performed a thorough self-review of my changes.
• I have added inline comments in complex or critical logic blocks.
• My changes introduce no new lint errors or compiler warnings.
• I have added corresponding test coverage for new execution paths.

Known Follow-up / Out of Scope

• This PR does not modify PR fix: stabilize CLI setup developer experience #8's code or Docker setup behavior.
• Full Python test suite is not relevant for this Markdown-only repository hygiene change.

[mrdanielcasper]

This is an improvement, but let's remove the quality gates run section and make the manual verification component a description of what steps were taken for local e2e / user validation. I'm finding, especially with LLMs, that I need to pull the levers (until we get a better eval strategy)