Add repo docs for agent guidance

docs/coding-standards.md

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+# Coding Standards
+
+These rules apply to Walkup-specific work in this repository.
+
+## General
+
+- Prefer the smallest change that fully solves the problem.
+- Preserve existing behavior unless the task explicitly requires a change.
+- Keep control flow straightforward and naming explicit.
+- Avoid broad refactors unless they are necessary to complete the task.
+
+## Frontend
+
+- Match the existing Bootstrap-based UI patterns.
+- Use Bootstrap Icons for iconography rather than custom SVG drawing.
+- Keep interactive controls readable and compact, especially in menus and toolbars.
+- Prefer UI changes that fit the current layout and spacing conventions.
+
+## Backend
+
+- Keep route handlers thin and push shared logic into helper functions when it improves clarity.
+- Treat tests as part of the implementation for non-trivial behavior changes.
+- Preserve API shape unless the change requires a contract update.
+
+## Testing
+
+- Add or update tests for user-visible behavior changes.
+- Run the smallest useful verification first, then broader checks for the touched area.
+- If a change cannot be covered automatically, call out the gap clearly.
+
+## Git And Workflow
+
+- Work on a dedicated branch for a scoped change.
+- Use the `Codex <codex@local>` identity for agent-authored commits.
+- Keep commits focused and reviewable.
+- Do not mix unrelated changes into the same commit.
+
+## Docs
+
+- Keep `docs/architecture.md` aligned with the current app structure.
+- Keep `docs/coding-standards.md` aligned with actual repo practice.
+- Update `PLAN.md` when work is completed, deferred, or split.