Add shared instruction files and copilot history maintenance scripts

- Add 12 cross-project instruction files to resources/instructions/
- Add cleanup-copilot-history.mjs/.sh: quarantine-based history cleanup with dry-run and aggressive scope
- Add restore-copilot-history.mjs/.sh: restore from quarantine by run, path, or filter
- Add purge-copilot-history-quarantine.mjs/.sh: purge old quarantine runs with keep-latest guard
- Add copilot-history-maintenance.test.mjs: 3 passing unit tests covering all three scripts

resources/instructions/vue.instructions.md

@@ -0,0 +1,14 @@
+---
+name: "Vue Standards"
+description: "Cross-project Vue standards for component structure, state derivation, and rendering efficiency."
+applyTo: "**/*.vue"
+---
+
+- Prefer Composition API with `<script setup>` for new components.
+- Keep components single-purpose and move reusable logic to composables.
+- Prefer computed state over watchers when deriving values.
+- Use props/events for communication instead of tight coupling.
+- Keep templates declarative; avoid embedding business logic in templates.
+- Minimize reactive dependencies and avoid broad reactive objects when narrower refs suffice.
+- Use lazy loading and route-level splitting when project architecture supports it.
+- Validate with the project's Vue lint/test/build commands.