Add per-session MCP debugger

[0xtlt]

Summary

• add admin-only debug sessions scoped to one access token, with pause, continue, and stop controls
• capture every gateway tool call in the selected session, including timing, original input/output byte counts, errors, and redaction state
• add a responsive flamegraph-style timeline with a focused call-details dialog that preserves the full timeline width and becomes fullscreen on mobile
• keep sensitive values redacted, exclude paused time from the trace clock, and discard delayed writes after a session state change
• add a real-timestamp migration, generated schemas/routes, documentation, and lifecycle/logging coverage

Validation

• pnpm test — 150 passing
• pnpm run lint
• pnpm run typecheck
• pnpm run build
• fresh migration run on SQLite
• responsive browser QA at 375 px, 768 px, and 1440 px, including success and error details
• independent diff review — no actionable findings

Demo

An updated demo upload is pending because the required mp4uploadcli command/configuration is not available on this runner; no video files are committed.