refactor(events): add typed IPC contracts for compile-time safety

[afonsojramos]

Summary

Adds an EventContracts type map keyed by every IPC channel ({request, response}) and makes handleMainEvent, invokeMainEvent, sendMainEvent, onMainEvent, sendRendererEvent, and onRendererEvent generic on the event key. Handler return types and renderer call sites are now compile-checked against the same single source of truth in src/shared/events.ts.

This is the only layer that would have caught #2839's decryptStringAsync regression at tsc time. Any future drift between IPC handler signatures and renderer expectations now fails the build instead of shipping.

What it catches

Verified with deliberate breakages — all error at compile time:

• Handler returning the wrong type (number for an event whose response is string).
• Handler returning an object when contract says string (the exact chore(deps): update electron to v42 and migrate to async safeStorage #2839 bug).
• invokeMainEvent called with extra args on a no-payload event.
• invokeMainEvent called with no args on a payload-required event.
• sendMainEvent called with the wrong arg type.
• New event added to EVENTS without a contract entry — AssertEventCoverage fires.

Notable changes

• Drops invokeMainEventWithData (subsumed by the now-generic invokeMainEvent).
• Drops the manual as Promise<IKeyboardShortcutResult> cast at the keyboard-shortcut call site.
• Drops the runtime as IKeyboardShortcut cast inside system.ts.
• Inlines the gitify: event prefix as a literal so EVENTS.* values are literal types.

Test plan

• pnpm tsc --noEmit passes.
• pnpm test — 933/933 (renderer route timeouts are a preexisting flake; they pass on retry and when run in isolation).
• pnpm lint:check — 0 errors.
• Manual contract drift verification: 6 deliberate breakages, all caught.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud