CadenceGovernor + time-series self-monitoring (ADR-0009)

[filipeforattini]

What to build

Add a CadenceGovernor that shapes per-host/identity request timing with human-like structure (reading dwell, inter-request jitter, session length + breaks, optional circadian pacing), bounded below by the politeness rate limiter and scaled by the PolicyProfile. Observed cadence is written to the crawl-events time-series and self-monitored (burstiness/frequency thresholds) to back off when the pattern looks bot-like. Cadence state lives in the StealthProfile. See ADR-0009.

Acceptance criteria

• Request timing is shaped per host (dwell/jitter/session breaks), never faster than the politeness floor.
• Shaping scales with PolicyProfile (fast disables, forensics maximises).
• Observed cadence is written to the time-series and a burstiness self-check backs off when anomalous.
• Tests cover pacing bounds and the self-monitor back-off.

Blocked by

• Coherence-aware StealthProfile priming + burn (ADR-0008) #71