WS-04: migrate daemon session runtime logging to slog

[glittercowboy]

TL;DR

• migrates the session runtime logging path onto structured slog
• removes ad-hoc logging inconsistencies from the daemon session manager / actor loop
• keeps daemon operational debugging aligned with the broader WS-04 observability work

What changed

• replace mixed logging calls in the daemon loop, session actor, and session manager with structured slog
• preserve the same operational events while making fields grep-friendly and consistent

Why it matters

• daemon reconnect, session isolation, and long-running task debugging are hard enough already; the runtime should emit consistent structured logs
• this keeps daemon-side readiness work aligned with the relay/web logging changes landing alongside WS-04

How it works now

• session lifecycle events now flow through the daemon logger consistently
• fielded slog output makes downstream collection/search more predictable

Verification

• go test ./...

Post-merge / deploy notes

• this repo change is independent from the cloud repo PR and can merge anytime
• if a new daemon release tag is required for deployment, cut/tag it after merge per the normal daemon release flow

Residual risk

• this PR improves observability only; it does not change daemon protocol behavior