chore: add squad directives for branching workflow and flake8 pre-push

Author: MDUYN

.squad/decisions/inbox/copilot-directive-2026-03-11-feature-branches.md

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+### 2026-03-11T12:00:00Z: User directive
+**By:** marcvanduyn (via Copilot)
+**What:** Always create a feature branch (`feature/*`) or fix branch (`fix/*`) for issue work. Never commit directly to `dev`. Push the branch, then open a PR into `dev`.
+**Why:** User request — maintain clean Git workflow with proper branch-based development.

.squad/decisions/inbox/copilot-directive-2026-03-11-flake8-before-push.md

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+### 2026-03-11T12:15:00Z: User directive
+**By:** marcvanduyn (via Copilot)
+**What:** Always run `flake8 ./investing_algorithm_framework` before pushing any changes. Fix any lint errors before committing.
+**Why:** User request — ensure code quality and style consistency.