[Feature] Replace void unused-result with explicit fire-and-forget comment + lint rule

[pathosDev]

Size / Priority

• Size: Trivial (~30+ sites)
• Category: C.2 Simplifications & DRY.
• Risk: low.

Affected files

• Across the codebase — sites using void this.foo() to mark fire-and-forget Promise calls.

Background

JavaScript Promise gotcha: an unawaited Promise that rejects produces an unhandled-rejection. TypeScript's no-floating-promises lint rule warns on this.

The conventional workaround is void promise to signal "I'm intentionally ignoring this":

void this._dispatchOne(env);   // fire-and-forget — caller doesn't await

The pattern is fine but appears ~30+ times without consistent comments. A casual reader doesn't always understand whether void was added to suppress a lint warning or because the Promise's rejection is being silently swallowed (which is a bug — should always be caught).

Target

Convention:

• void promise; /* fire-and-forget */ with explicit comment — preferred.
• promise.catch(e => this.log.warn(...)) — when rejection should be logged.
• Custom helper for repeated patterns:

// src/util/Async.ts (new)

/** Run a Promise fire-and-forget with a logging fallback. */
export function fireAndForget<T>(p: Promise<T>, label: string, log: Logger): void {
  p.catch(e => log.warn(`[fire-and-forget] ${label}: ${(e as Error).message}`));
}

Lint rule: enforce that void is accompanied by a comment OR the Promise is .catch()-handled.

Integration / risk

• No behavioural change.
• Helps reviewers spot accidentally-swallowed errors.

Test plan

1. Lint configuration update.
2. Per-site review: each void promise documented or migrated to fireAndForget.

Acceptance criteria

• Lint rule for void Promise documented.
• fireAndForget helper exported.
• All sites either commented or migrated.
• No CHANGELOG entry needed.