docs: plan daemon-logging

[ArthurBernard]

Goal

Make the daemon auditable from its log alone. The 2026-07-14 health audit had to reconstruct everything from the API and the SQLite books: logs/daemon.log is a bare shell redirect of untimestamped rich prints — no per-unit lines, no order/skip trail, no rotation, 10 process incarnations interleaved. Key evidence: the runner already logs prepare_leg decisions at DEBUG with no configured handler (invisible), and the realised tick cadence was ~74 s vs the nominal 60 s with add_job carrying no explicit misfire semantics.

Adds the 3b. roadmap index line (Road to v1.0.0 — prereq for #4's systemd alerting + soak evidence).

Leaf checklist

• 01 log-setup — feat/daemon-log-setup — medium — LoggingConfig (level/dir/retention), midnight-rotated TimedRotatingFileHandler, ISO-8601 timestamps with tz offset, lifecycle lines + tracebacks routed through it
• 02 unit-event-trail — feat/daemon-unit-event-logs — medium — rebalance summaries, round-up/skip LegDecision.reason at INFO, order submit/fill lines with cids; pinned anti-spam rule (no-new-bar tick = zero INFO lines)
• 03 tick-timing-metrics — feat/tick-timing-metrics — medium — tick/unit durations logged (WARN on overrun), explicit coalesce/misfire_grace_time/max_instances, additive /api/health + /api/strategies timing fields

Strictly serial (01 → 02 → 03 — shared files: supervisor.py, cli/main.py). Every leaf verifies on a scratch instance (port 8099, scratch book copies, read-only dccd store) — the live daemon on port 8000 is never touched; the legacy unrotated log gets archived at the post-release prod restart (runbook note in 00-plan.md).

Test plan

• docs-only PR (plan tree + roadmap index line)
• CI green