chore: add cursor agent rules

.cursor/rules/learn-technical.mdc

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+---
+description: Capture technical lessons learned into cursor rules
+alwaysApply: true
+---
+
+# Technical Learnings
+
+When you discover a technical pattern, gotcha, or convention specific to this codebase, create or update a rule in `.cursor/rules/` to capture it.
+
+Examples of technical learnings worth capturing:
+
+- ORM differences between SQLAlchemy and Django models (field names, method names, enum types)
+- Import conventions (canonical locations for shared enums, models, constants)
+- Compatibility gotchas (e.g. `TextChoices` vs plain `Enum`, `cached_property` vs `property`)
+- Test patterns (which factories to use, which fixtures, `@pytest.mark.django_db`)
+- Architecture decisions (where shared code lives, what belongs in `libs/shared/` vs `apps/worker/`)
+
+Write the rule as a concise reference — something a developer (or agent) can consult mid-task. Include concrete examples where possible.

.cursor/rules/learn-workflow.mdc

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+---
+description: Capture workflow lessons learned into cursor rules
+alwaysApply: true
+---
+
+# Workflow Learnings
+
+When you discover a workflow pattern that should be repeated — or a mistake that should be avoided — create or update a rule in `.cursor/rules/` to capture it.
+
+Examples of workflow learnings worth capturing:
+
+- A git workflow that worked well (e.g. how to structure stacked PRs)
+- A step that was missed and caused rework (e.g. forgetting to run linters)
+- A review or PR convention the team expects
+- A process for splitting, sequencing, or batching changes
+
+Write the rule as a concise, actionable instruction — not a story of what happened. Future agents should be able to follow it without context.

.cursor/rules/pre-commit-checks.mdc

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+---
+description: Run pre-commit checks (ruff lint + format) before creating PRs or commits
+alwaysApply: true
+---
+
+# Pre-commit Checks
+
+Before creating a PR or making a commit, always run the project's pre-commit hooks to catch lint and formatting issues:
+
+```bash
+ruff check --fix .
+ruff format .
+```
+
+If either command produces changes, stage the fixes and include them in the commit.
+
+This project uses `ruff` for both linting (`ruff check`) and formatting (`ruff format`), configured in `pyproject.toml` and enforced via `.pre-commit-config.yaml`.

.cursor/rules/small-prs.mdc

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+---
+description: Break large changes into small, focused PRs
+alwaysApply: true
+---
+
+# Small, Focused PRs
+
+When a task involves multiple logical changes, split them into separate PRs rather than one large PR.
+
+## Guidelines
+
+- Each PR should do **one thing**: a single refactor, a single consolidation, a single feature addition.
+- If a set of changes naturally stacks (B depends on A), create stacked PRs with the base set to the previous branch.
+- Aim for PRs that are **easy to review in one sitting** — a reviewer should be able to understand the intent from the title alone.
+
+## Examples of good splits
+
+- Moving definitions to a new location (bulk import change) = 1 PR
+- Consolidating a duplicate enum/constant to its canonical source = 1 PR per enum
+- Adding a new method to a model + migrating callers to use it = 2 PRs
+
+## When creating stacked PRs
+
+1. Create a branch per logical change, each based on the previous.
+2. Push all branches.
+3. Open draft PRs with each PR's base set to the previous branch.
+4. Note the dependency in the PR body (e.g. "Stacked on #123").