Harden stats APIs and fix Electron Yomitan debug runtime

- Validate stats session IDs/limits and add AnkiConnect request timeouts
- Stabilize stats window/runtime lifecycle and tighten window security defaults
- Fix Electron CLI debug startup by unsetting `ELECTRON_RUN_AS_NODE` and wiring Yomitan session state
- Expand regression coverage for tracker queries/events ordering and session aggregates
- Update docs for stats dashboard usage and Yomitan lookup troubleshooting

docs-site/character-dictionary.md

@@ -4,6 +4,23 @@ SubMiner can build a Yomitan-compatible character dictionary from AniList metada
 
 The dictionary is generated per-media, merged across your recently-watched titles, and auto-imported into Yomitan. When a character name appears in a subtitle line, it gets highlighted and becomes available for hover-driven Yomitan profile lookup.
 
+## Stats Dashboard
+
+The character dictionary and stats dashboard both read from the same local immersion data.
+
+- Open the dashboard from overlay: press your configured `stats.toggleKey` (default: `` ` `` / `Backquote`).
+- Open from launcher/CLI: run `subminer stats`.
+- Open directly: visit `http://127.0.0.1:<stats.serverPort>` when the local server is running.
+
+Useful config keys:
+
+- `stats.autoStartServer` — start the local stats server automatically once immersion tracking starts.
+- `stats.serverPort` — local HTTP port for dashboard and API.
+- `stats.toggleKey` — key binding for overlay dashboard toggle.
+- `stats.autoOpenBrowser` — auto-open dashboard browser for `subminer stats`.
+
+The dashboard gives quick visibility into episode summaries, watch-time rollups, session timelines, and vocabulary/kanji drill-down from the same DB used by character matching.
+
 ## How It Works
 
 The feature has three stages: **snapshot**, **merge**, and **match**.