feat(observability): pipeline-aware metrics, dashboard, and printer column

[amcheste-ai-agent]

Summary

Knowledge-work teams operate at the granularity of pipeline stages
and produced artifacts, not just tokens and cost. Observability
needed to match — operators should be able to see, at a glance, which
stage a team is in, how long stages take, what came out the other
end, and whether delivery to external systems worked.

This PR adds five new metrics under the kagents_ prefix, a dashboard
pipeline section, an artifact listing, a kubectl Stage printer column,
and the corresponding tests.

New metrics (kagents_ prefix)

Metric	Type	Labels
kagents_team_pipeline_stage_active	gauge	team, namespace, stage
kagents_team_stage_duration_seconds	histogram	team, namespace, stage
kagents_team_artifacts_produced_total	counter	team, namespace, teammate
kagents_team_delivery_success_total	counter	team, namespace, type
kagents_team_delivery_failure_total	counter	team, namespace, type

Dual-prefix decision

The existing claude_* family stays untouched so existing dashboards
keep working. This PR adds the new metrics alongside; a future major
release can synchronize the prefixes. Documented in
docs/explanation/operations.md.

Reconciler wiring

• updatePipelineStatus emits the stage gauge on every reconcile
  (Running → 1, otherwise 0) and observes duration exactly once at
  the Completed transition (gated on prevPhase != Completed).
• recordTeammateArtifacts increments the artifact counter inside
  the dedup-checked append path — idempotent across reconciles.
• executeDelivery records success vs failure per target alongside
  the existing event emission.

kubectl

New Stage printer column (priority=1, so it shows on kubectl get agentteams -o wide / wide terminals). Sources
status.pipeline.currentStage.

Dashboard

• Pipeline section on the team detail view: progress bar over
  completed/total stages, list of stages with phase chip + teammates-ready
  ratio.
• Artifacts section listing name, producing teammate, and source path;
  renders only when status.artifacts is non-empty.
• New pipelinePercent template helper, fully covered (nil, zero,
  half, full, overflow clamp).

Tests

• internal/metrics → 100% coverage. Five new tests plus the
  names-guard extended to the new prefix.
• internal/dashboard → 73.9% with new helper tests.
• internal/controller — existing pipeline-status tests stay green.

Test plan

• CI green
• kubectl get agentteams -o wide shows the Stage column

🤖 Generated with Claude Code