feat(perf): implement performance optimizations for session handling

- Introduced a new configuration file `config.yaml` for specifying project context and artifact rules.
- Added `.openspec.yaml` files for tracking changes related to performance improvements.
- Created design documents outlining the context, goals, decisions, and migration plans for optimizing session performance.
- Proposed changes include batching database queries, debouncing event refreshes, purging old events, and implementing loading states for better user experience.
- Added tasks and specifications to ensure proper implementation and validation of the new features.

These enhancements aim to improve the scalability and responsiveness of the application during collaborative sessions.

openspec/changes/perf-realtime-scale/specs/sse-shared-polling/spec.md

@@ -0,0 +1,17 @@
+## ADDED Requirements
+
+### Requirement: Single polling interval per active session
+The SSE infrastructure SHALL maintain at most one active DB polling interval per session, regardless of the number of connected clients.
+
+#### Scenario: First client connects starts polling
+- **WHEN** the first client connects to a session's SSE endpoint
+- **THEN** a single polling interval SHALL be started for that session
+
+#### Scenario: Additional clients share existing polling
+- **WHEN** a second or subsequent client connects to the same session's SSE endpoint
+- **THEN** no additional polling interval SHALL be created
+- **THEN** the new client SHALL receive events from the shared poll
+
+#### Scenario: Last client disconnect stops polling
+- **WHEN** all clients disconnect from a session's SSE endpoint
+- **THEN** the polling interval for that session SHALL be stopped and cleaned up