Release v0.4.0

What's changed

Added

• IDE plugin header support — X-Audit-User, X-Audit-Team, X-Audit-Project, X-Audit-Branch, X-Audit-Session-ID, and X-Audit-Agent headers allow IDE companion plugins to inject per-request identity and context; header values override env-var defaults (AUDIT_PROJECT, AUDIT_BRANCH) for centrally-hosted deployments
• Unprocessed events table — responses the proxy cannot parse into structured audit records (non-chat endpoints like /v1/models and /v1/count_tokens, unknown providers, parse errors) are routed to audit.unprocessed_events instead of being silently dropped; stores raw body, HTTP method, path, status code, content type, and parse error message
• Health endpoint — GET /healthz returns {"status":"ok","version":"..."} for IDE plugin connectivity checks and load balancer probes; version set at build time via -ldflags "-X main.version=..."
• user and team columns on audit_events — LowCardinality(String), populated from X-Audit-User and X-Audit-Team headers
• UnprocessedAdder interface and UnprocessedBatcher — mirrors EventAdder/Batcher pattern for the unprocessed events write path
• ANTHROPIC_UPSTREAM_URL, OPENAI_UPSTREAM_URL, GEMINI_UPSTREAM_URL env vars — override the default upstream target for each provider without changing detection logic; useful for routing through LiteLLM, Portkey, a regional endpoint, or any internal gateway
• NewRouterWithConfig(RouterConfig) constructor on Router — accepts upstream URL overrides alongside SAP AI Core config; NewRouter preserved as backwards-compatible wrapper
• Migration 005_add_user_team.sql — adds user and team columns to existing installations
• Migration 006_unprocessed_events.sql — creates the unprocessed_events table
• Cline agent detection — detectAgent now matches cline in the User-Agent header
• Claude Code VSCode extension detection — detectAgent now matches claude-cli User-Agent sent by the VSCode extension (in addition to claude-code from the CLI)
• Session ID priority chain: X-Audit-Session-ID > X-Session-ID > auto-generated UUID
• IDE plugins design document (docs/ide-plugins-design.md) — comprehensive design for VSCode and JetBrains companion plugins covering env var injection, config file schema, and header protocol
• New handler tests: X-Audit-* header overrides, session ID fallback, Cline detection, Claude VSCode extension detection, unprocessed event routing

Changed

• extractEvents now returns ([]audit.AuditEvent, error) instead of []audit.AuditEvent — parse errors are surfaced to the caller for routing to the unprocessed table
• NewHandler signature extended with unprocessed audit.UnprocessedAdder parameter
• requestMeta struct extended with user, team, method, and unprocessed fields