docs: add local verification steps to CONTRIBUTING

[kshivam4781]

Closes #17.

What

Adds a "Local verification" section to CONTRIBUTING.md, placed right after the existing "Pre-commit" section, so a first-time contributor can pick the right checks for the kind of change they made instead of guessing or running everything.

Why

CONTRIBUTING.md documented individual commands but never said which ones apply to a docs-only change vs. a frontend change vs. a backend change, and it didn't mention the Playwright specs under frontend/e2e/ at all. The new section covers all four cases called out in the issue:

• Documentation-only change: no command required, just proofread.
• Backend change: the existing uv run ruff check ... / PYTHONPATH=backend uv run pytest -q commands (matches .github/workflows/ci.yml's test job).
• Frontend change: the existing pnpm --filter agent-improvement-console-ui run lint / run build commands (matches the frontend job in .github/workflows/ci.yml).
• UI end-to-end change: explains that the frontend/e2e/ Playwright specs are not run in CI and need the app running locally plus hand-prepared sample data, so a contributor doesn't assume a green compile means the spec passed.

No application behavior or CI configuration changed, per the issue's acceptance criteria.

Verification

Ran all of the commands the new section documents, from a clean clone, before writing them down:

• uv run ruff check orbit/ backend/ tests/ — all checks passed
• PYTHONPATH=backend uv run pytest -q — 44 passed
• pnpm --filter agent-improvement-console-ui run lint — clean
• pnpm --filter agent-improvement-console-ui run build — built successfully

I did not run the frontend/e2e/ Playwright specs against a live instance — per the issue and the new section itself, they need a locally running app plus specific sample evaluation builds created by hand, which is exactly the manual step the doc change is describing rather than something this change automates.

Rendered the section with the GitHub Preview tab to confirm the Markdown (bold labels, code fences) renders as intended before opening this PR.

[forthfate]

@kshivam4781 Thank you again for this thoughtful contribution, especially at such an early stage of OpenOrbit. The local verification breakdown is very helpful.

One small wording suggestion: frontend linting is configured in the local pre-commit hook, but the current CI frontend job only runs the production build. Could we make that distinction clear in the introductory sentence?

Please also update the branch with the latest main when you have a chance. Thanks!

[forthfate]

@kshivam4781
Sorry to push, but how are things coming along?