feat(operator): add delayed Slack personal replies

[edwin-zvs]

Summary

• add the auto-after Slack personal response mode with a configurable auto_after_secs grace period
• wait after reply generation, re-read the thread, and silently yield when the account owner replied first
• expose parsing, validation, summaries, TUI/web configuration, and safe defaults
• update spec 0202 to make the delayed auto-send contract explicit
• integrate merged adaptive polling from PR feat(operator): adapt Slack personal polling cadence #1275: poll_interval_secs remains the idle ceiling while auto_after_secs controls reply grace

Verification

• cargo test -p construct-daemon operator:: (124 passed)
• cargo test -p construct-cli operator_channel_editor_cycles_to_slack_personal_with_safe_defaults (passed)
• embedded web UI JavaScript node --check (passed)
• cargo build --workspace (passed)

No recording: this is primarily operator-channel configuration/runtime behavior; the small editor additions are covered by the existing TUI test.