feat(observability): emit session usage threshold events for prompt turns and context%

[Yeachan-Heo]

Summary

Add explicit OMC/OMX session observability events for usage thresholds (prompt turns, context-used %, and similar runtime metrics) so clawhip can send reliable alerts without brittle tmux text scraping.

Why

We already have clawhip handling lifecycle-style notifications well (started / finished / failed / stale / keyword hits). But alerts like:

• prompt turn count crossing N
• context-used % crossing 70 / 85 / 92
• maybe long-running + high-context sessions

should come from the runtime itself, not from parsing tmux pane text. Scraping pane output would be brittle, fail-open, and sensitive to HUD/output wording changes.

Desired behavior

When an OMC or OMX session crosses configured thresholds, emit a structured event that clawhip can route to Discord.

Examples:

• session.turn-threshold
• session.context-threshold

Example payload shape:

{
  "project": "omc",
  "session": "omx-pr-2139-review",
  "metric": "context_percent",
  "value": 72,
  "threshold": 70,
  "severity": "warning",
  "reason": "context_warning"
}

Scope

In OMC / OMX

• Identify the runtime/source-of-truth where prompt turns and context usage are already known
• Add thin threshold emitters there
• Avoid repeated spam after the same threshold fires unless a higher threshold is crossed
• Keep it opt-in/configurable if needed

In clawhip

• Route and render the emitted threshold events
• Support mention escalation based on severity (warning / alert / critical)

Suggested thresholds

• Prompt turns: 20 / 40 / 60
• Context used: 70 / 85 / 92

Acceptance criteria

• A session crossing a configured prompt-turn threshold emits one structured event
• A session crossing a configured context-used threshold emits one structured event
• Repeated polling/refresh does not spam duplicate events for the same threshold
• Higher thresholds can still fire later for the same session
• clawhip can route the events without parsing pane text

Notes

This should preserve a clean boundary:

• OMC/OMX = source of truth for session/runtime metrics
• clawhip = notification router / formatter

—
[repo owner's gaebal-gajae (clawdbot) 🦞]